Psych Stats
Using inferential statistics to arrive at a conclusions about behavior means that
one makes a decision based on the probability that differences or relationships between variables exist in those not even tested as part of a study
A measure of how much knowledge of psychology students have gained during the semester, an instructor gives a 50-item multiple choice exam. The test grade (A, B, C, D, F) is an example of which scale of measurement?
ordinal
A person's class rank amongst their high school class is an example of which scale of measurement?
ordinal
Determining class standing for the graduating seniors at the high school would involve measurement of a(n) ___ scale of measurement?
ordinal
Determining the class standing for the graduating seniors at a high school would involve measurement on a (n) ____ scale of measurement
ordinal
Interstates running from West to East have even numbers, with lower numbers in the South and higher numbers in the North. For example, I-40 runs through Arkansas, I-80 through Illinois, and I-90 through New York. This numbering system is an example of what scale of measurement?
ordinal
A group of researchers believed people's perceived economic status (high or low) would cause changes in their support for political policies that redistributed income. What was their independent variable?
perceived economic status
Dr. Spearmint conducts a study where she changes the room temperature and measures its effect on participant's performance on a simple task. What is his dependent variable?
task performance
A researcher is interested in the political orientation of UCA students. He distributes a social conservatism survey to 50 students. What is the sample?
the 50 students
Which of the following is an example of a descriptive statistics?
the mean of a sample of test scores
Inferential statistics are estimated of unknown information, so they always involve some degree of
uncertainty
The owner of Betty's Machetes conducts a survey with a sample of 25 of her customers to see the mean (average) satisfaction rating for their last machete purchased. If she wants to see if she can generalize the results to the larger population of customers, she should
use both descriptive and inferential statistics
Which of the following is a continuous variable?
weight
In a class of 40 students, there are 10 males and 30 females. Half of the class is psychology majors, 2 of whom are males. If a student is selected at random, what is the chance that they are either male or a psychology major (or both)?
8/40
If the standard deviation of a dataset is 9, what is the variance?
81
What is a sample mean often treated as an estimate of?
A population mean
What is the sample mean often treated as an estimate of?
A population mean
When high scores on one variable occur with high scores on another, and low scores occur with low scores, their correlation coefficient will be somewhere between________ and ________
0 and 1
R-squared as a measure of effect size will always have a value in the range ___ and indicated the ____.
0-1; proportion of variance accounted for
There are 4 aces in a standard deck of 52 cards. What is the probability of drawing 2 aces in a row without replacement (the first card drawn does not go back in the deck before the second draw)?
0.0045 4/52 * 3/51
A 95% confidence interval is most commonly used when the alpha level is
0.05
In a class of 40 students, there are 10 males and 30 females. Half of the class is psychology majors, 2 of whom are males. If a student is selected at random, what is the chance that they are a male psychology major?
0.05
In a class of 40 students, there are 10 males and 30 females. Half of the class is psychology majors, 2 of whom are males. If a psychology major is selected at random, what is the chance that they are male?
0.1
A sample of 16 scores provides a mean of 12 and a standard deviation of 8. If the null hypothesis states that the population mean is 10, what is the value of Cohen's d?
0.25 12-10/8
A researcher finds that neuroticism and self-reported number of close friends are significantly correlated, r = -.7. What is the effect size for this correlation?
0.49
A treatment is administered to a sample selected from a population with a mean of = 80 and a standard deviation of = 10. After treatment, the sample mean is M = 85. Based on this information, the effect size as measured by Cohen's d is
0.5
For Cohen's d, which of the following would be considered a moderate effect size?
0.51
In a normal distribution, the probability of getting a score below a z-score of 3 is...
0.9987
A set of 30 exam scores with a mean of 60 and a standard deviation of 5 is converted to z-scores. What will be the variance of the transformed scores
1
Over a number of days, you measure the outside temperature with two thermometers, one that provides the temperature in degrees Celsius and the other that provides the temperature in degrees Fahrenheit. The correlation between the readings from the two thermometers would be
1
If a distribution has two scores that are tied for most common, which is the mode?
Both scores are the mode
If a distribution has two scores that are tied for the most common, which is the mode?
Both scores are the mode
For a perfectly symmetrical normal distribution, which relationship is always true?
Mean = median = mode
A researcher reports that the size of an effect in some population is d=0.88. Which of the following is an appropriate interpretations for d?
Mean scores shifted 0.88 standard deviations in the population
Suppose a class takes a quiz and the majority of scores are high with a few low scores. Which is the most likely shape of the distribution?
Negatively skewed
The course numbers for 2000-level courses (ex: MATH 2331) are which scale of measurement?
Nominal
Whether or not someone is in the experimental group or the control group in a study represents which scale of measurement?
Nominal
Bar graphs are used to represent the frequency for which type of variables?
Nominal and Ordinal
The Yerkes-Dodson law states that moderate levels of physiological arousal are related to optimal performance. Arousal levels higher or lower than this optimal level produce poorer performance. Given this, you would expect Person r to be
close to zero
An example of a variable measured on an ordinal scale is
college classification (freshmen, sophomore, etc)
A researcher has participants rate their overall happiness on scale of 1(extremely unhappy) to 10(extremely happy) to see how this relates to their GPA. We would describe the underlying variable of happiness as ___________ and the specific way that we are measuring it as ____________.
continuous, discrete
As a measure of how much knowledge of psychology students have gained during the semester, an instructor gives a 50-item multiple choice exam. "Knowledge" is an example of what type of variable?
continuous, quantitative
An important concept in correlational research is that
correlation does not imply causation
The purpose of a scatterplot is to
create a graph of a relationship between two variables that visually represents both the direction and strength of the relationship
Other things held constant, as you increase sample size, the shape of the sampling distribution of the mean will
decrease
As sample size increases, the standard error of the mean
decreases
A doctor studies a very rare disease with only five known cases. The doctor wants to know the average age of onset of the disease and because he is the doctor for all five cases, he can simply look at their medical records. This doctor would likely perform.
descriptive statistics only
The most important reason for determining a variable's scale of measurement is to
determine which type of statistical analyses are appropriate to use
The distance an individual score is from the mean is called
deviation
the distance an individual score is from the mean is called
deviation
Why are deviation scores not useful measures of variability in a sample?
deviation scores across a sample will always add up to 0
Which of the following is true of scatterplots?
each single point shows one participant's scores on two variables at once
___ allows researchers to describe (1) how far mean scores have shifted in the population or (2) the percentage of variance that can be explained by a given variable
effect size
Which of the following represents a situation where you might use inferential statistics?
When you collect data from a sample but want to use their mean to make an estimate about the mean of the entire population
A researcher gives 10 people a strong cup of coffee, and another 10 a cup of decaf. He then measures their heart rate. What is the independent variable?
Whether or not the people drank regular or decaf
Which of the following studies would best be analyzed with an independent samples t-test
You randomly assign children with a diagnosis of ADHD to two different treatment groups and then compare the two groups on their academic success in class for the month
Suppose you find out that your z-score on an exam is +3.00. Which of the following is true?
Your score was higher than most of the other student's scores
Which confidence interval would lead one to NOT reject the null hypothesis that the population mean is zero? (Assume that the probability of a Type I error is set at 5%)
a 95% confidence interval from -2 to 5
An independent samples t-test is appropriate for what type of research design?
a between-participants design
A good analogy for a type I error is
a blood test incorrectly indicating that a person has Lycanthropy
A good analogy for a type II error is
a blood test incorrectly indicating that person does not have Lycanthropy
You measure a person's shoe size and their GPA and find no significant relationship between these two variables. Your best guess as to the visual pattern of points on the scatterplot would be
a circle of points without any obvious tilt to them
If rejecting the null is thought of as a "positive" test result and failing to reject it a "negative", a Type I error could also be called
a false positive
A researcher is interested in testing whether introverts (shy people) or extraverts (outgoing people) have better short-term memory. Introversion/Extraversion is
a quasi-independent variable
For a research study comparing attitude scores for males and females, participant gender is an example of what kind of variable
a quasi-independent variable
How will a negative correlation appear on a scatterplot
a straight line that slopes downward
A vertical line is drawn through a normal distribution at z= 1.00. The line separates the distribution into two sections and the larger section corresponds to _____ of the whole distribution.
about 84%
A researcher is interested in the political orientation of UCA students. He distributes a social conservatism survey to 50 students. What is the population?
all UCA students
The distribution of sample means (for a specific sample size) consists of
all the sample means that could be obtained (for the specific sample size)
Which of the following statements about the alpha level of a hypothesis are not true? -alpha level determines the size of the region of rejection (critical region) -alpha level determines whether you are conducting a 1-tailed or 2-tailed test -alpha level determines the maximum p-value that will allow the researcher to reject the null hypothesis -alpha level is usually set at .05 or .01
alpha level determines whether you are conducting a 1-tailed or 2-tailed test
Confidence intervals are most often used as
an inferential statistic to supplement null hypothesis testing
Which of the following accurately describes a hypothesis test?
an inferential technique that uses data from a sample to make conclusions about a population
which of the following accurately describes a hypothesis test
an inferential technique that uses data from a sample to make conclusions about a population
The hypothesis test
an inferential technique that uses the data from a sample to draw inferences about a population
Dr. Lashun finds amount of sleep and reaction time are correlated at r = -.28. Which of the following best describes this relationship?
as sleep increases, reaction time tends to decrease
Dr. Lashun finds words typed per minute and reading comprehension are correlated at r = .45. Which of the following best describes this relationship?
as words typed per minute decreases, reading comprehension tends to decrease
A graph representing the number of majors in each department within the College of Health and Behavioral Sciences would be a
bar graph
A physical therapist measures how many times male participants can life a 40 lb weight compared to female participants. What should she use to graph the comparison?
bar graph
You conduct a study and find a negative correlation between a child's relationship with their teacher and the number of disciplinary referrals to the principal's office. The most appropriate conclusion is that
children with better teacher relationships also tend to have fever disciplinary referrals
You decide to collect information on weight for a sample of 500 people. Which type of graph would be best to use in this scenario?
either a histogram or frequency polygon
In a normal distribution, you have the highest probability of selecting scores that are
equal to the mean
A Type I error means that a researcher has
falsely concluded that a treatment has an effect
A type II error means that a researcher has
falsely concluded that a treatment has no effect
For the past 20 years, the high temperature on April 15th has averaged = 62 degrees with a standard deviation of = 2. Last year, the high temperature was 68 degrees. Based on this information, last year's temperature on April 15th was
far above average
When reporting household incomes for a geographical region, the median is preferred over the mean. This is because
household incomes likely represent a skewed distribution
If you calculate the 95% confidence interval for a sample mean, you know that
in repeated sampling, the true population mean would fall in the given interval 95% of the time
What is one way to decrease the standard error of the mean
increase the sample size
The type of treatment used in a research study describes the
independent variable
The term "inferential" is appropriate because we
infer about the characteristics of a population based only on a sample
Hypothesis testing is a(n)
inferential method for determining whether a population parameter has a particular value
Most often, when you arrive at a conclusion about your study's hypothesis, the last step in the statistical analysis requires
inferential statistics
The larger the level of confidence, the ___ precise the interval estimate
less
If there is less variability of scores in your population, then you would expect
less sampling error
The variability of the sample means in a sampling distribution will always be
less than the variability of scores in the population
Quasi-experimental study
looks just like experimental, but the researcher cannot control the variable, comparisons that are pre-existing groups ex: Gender, "difference between males and females"
In an experiment, the independent variable is ___ by the experimenter
manipulated
What statistic does not belong with the others -range -mean -SD -variance
mean
When you do a correlational study, you, as the researcher
measure two variables but do not manipulate (control) either one
The measure of central tendency that is the same as the 50th percentile is the
median
Which of the following pairs of variables should produce a negative relationship (correlation)?
number of hours studying and number of errors on a math exM
Which of the following pairs of variables should produce a zero correlation?
number of pets you've had and GPA
An example of a variable measure on a ratio scale is
number of random acts of kindness observed
What is the difference between a statistic and a parameter?
o Any value calculated on the basis of a population o Statistics uses English letters: M, S, D o Parameters tend to use Greek letters: Mu, Lambda
Statistical research
o Collecting (measuring or quantifying), organizing (structure), analyzing (interrogate), and interpreting (telling the story) numerical data
Descriptive statistics
o Organize and summarize a large amount of data in abbreviated, symbolic form o What is one example of a descriptive statistic? ▪ Mean, median, mode
Inferential statistics
o Procedures to draw conclusions about data o Make inferences or predictions about unknown values o What is one example of an inferential statistic? ▪ Bacon consumption related to heart disease, cancer, etc
Statistics
o Statistics are a way to evaluate "truth". o The point at which common sense meets logic o Numbers are used to convey ideas o Our data needs to be available to other researchers to advance the field o Numbers that characterize scores of a SAMPLE Statistics refers to: 1) The practice of making sense of data 2) The mathematical procedures to organize, summarize and interpret data 3) The numbers obtained from the procedures
Conceptually, the standard error of the mean tells you
on average, how far off your sample means are likely to be from the true population mean
If you scored at the 90th percentile on a test, you would know that
only 10% of the students who took the test scored higher than you
A statistics instructor calculates the standard deviation for a set of homework scores to see how much scores tend to differ. The instructor has used
only descriptive statistics
If a researcher is only interested in the data they've collected and not estimating any unmeasured scores they would need to use
only descriptive statistics
A Pearson correlation of r = +0.85 indicates that a scatterplot would show
points clustered close to a line that slopes up to the right
Heavier vehicles require more breaking distance than lighter vehicles. The correlation between the two would be
positive
If high scores on one variable are associated with high scores on another variable, this indicated a
positive correlation
If high scores on one variable are associated with high scores on another variable, this indicates a
positive correlation
If low scores on one variable are associated with low scores on another variable, this indicated a
positive correlation
If the bars on a histogram are highest when scores are lowest and much less frequent for higher scores, the shape of the histogram would be:
positively skewed
The power of a statistical test is best described as the
probability of finding a significant effect/relationship when ones in fact exists in the population
an advantage of the stem-and-leaf display over a histogram is that it
provides the original individual values
The most powerful way to create groups for an independent samples t-test is to
randomly assign participants to two different groups
The number of pets a person has represents which scale of measurement
ratio
To assess students' interest in class lectures, an instructor tracks daily attendance. Attendance (number of days present) would be an example of what scale of measurement?
ratio
many physical dimensions such as height, depth, and distance are ____ variables
ratio
If the null hypothesis is outside the confidence interval, then the decision was likely to ___ using hypothesis testing
reject the null hypothesis
If the z score for your treated sample mean is in the critical region of the sampling distribution, the most appropriate statistical decision is to
reject the null hypothesis
If the z score for your treated sample mean is NOT in the critical region, then the most appropriate statistical decision is to
retain the null hypothesis
The standard error is used instead of the standard deviation when examining
sample means rather than individual scores
In a hypothesis test, the critical region consists of
sample values that are very unlikely to be obtained if the null hypothesis is true
Descriptive statistics can describe the characteristics of a ___ while inferential statistics makes inferences about the characteristics of a ___
sample; population
Sir Francis Galton created a graph where the heights of parents were represented on the X-axis and the heights of their adult children on the Y-axis. Thus, each point on the graph represented a pair of parent/child heights. This type of graph is called a
scatterplot
Which of the following can correlations NOT be used to do?
show cause and effect between two variables
Dr. Spearmint conducts a study where she changes the size of written text and measures its effect on participant's reading comprehension. What is the independent variable?
size of text
What kind of distribution shape cannot be symmetrical?
skewed
Which of the following does not belong with the others? skewed bellshaped uniform symmetric
skewed
Based on the effect size conventions, d=0.18 is a
small effect size
The standard error of the mean is like the
standard deviation for the sampling distribution of means
The standard deviation for the distribution of sample means is called the
standard error
The best measure of sampling error is the
standard error of the mean
The measure of variability on a sampling distribution of the mean is the
standard error of the mean
Which of the following is most similar to a histogram?
stem and leaf plot
what do descriptive statistics allow us to do?
summarize the characteristics of a sample of scores
Which of the following is NOT a measure of effect size? -Cohen's d -R squared -t score -none of the above
t score
What is wrong with the following report of a Pearson r correlation coefficient: r (25) = 0.00, p < .05.
the Pearson r value of zero cannot have a probability value < .05
Standard deviation is best conceptualized as
the average distance of the scores from the mean
A standard deviation is conceptually most similar to what?
the average of all deviations from the mean
A researcher is interested in the political orientation of UCA students. He distributes a social conservatism survey to 50 students. What is the relevant statistic?
the average opinion of the 50 students
The Cohen's d effect size for your study with a new antidepressant medication is 0.5. The most appropriate interpretation is that
the drug showed a moderate effect in decreasing depression by a 1/2 of a standard deviation
A predicted effect is tested by a null significance hypothesis test, and a statistically significant result is found. Which of the following described the most appropriate conclusion to take from the test.
the effect is likely but not certain to exist in the population
As sample size increases, what happens to the mean and standard error of a sampling distribution?
the mean stays the same and the standard error decreases
A set of students is surveyed about their major, what is the best measurement of central tendency for this variable?
the mode
a therapist is investigating the impact of a new treatment for depression compared to an old treatment. Which of the following accurately represents the alternative hypothesis
the new treatment produces different results than the old one
A therapist is investigating the impact of a new treatment for depression compared to an old treatment. Which of the following accurately represents the null hypothesis.
the new treatment produces results that are similar to the old treatment
In a frequency distribution for a person's age, the height of the bar or curved line represents
the number of people of a particular age
What would be a reasonable null hypothesis for a two sample t test?
the population means are the same
What would be a reasonable null hypothesis for a two-sample t-test?
the population means are the same
The alpha level determines
the probability of a type I error
A problem with using the mode as a measure of central tendency is that
the same set of data can produce more than one mode
Which of the following is most likely to be found if a sample is randomly drawn from a population?
the sample mean is .01 standard errors from the population mean
Which of the following is least likely to be found if a sample is randomly drawn from a sample population?
the sample mean is 2.5 errors from the population mean
Which of the following is least likely to be found if a sample is randomly drawn from a population?
the sample mean is 2.5 standard errors from the population mean
If you sum up the frequency values in a frequency distribution, that number will tell you
the total number of scores in your sample
A researcher shows that a new treatment significantly reduces depression, with an r-squared of .25. What is the correct interpretation of this value?
the treatment accounted for 25% of the variance in depression
The mean of the sampling distribution of the mean is always equal to
the true population mean (or your best estimate of it)
What would be a reasonable alternative hypothesis for a two sample t test?
the two population means are different
What would be a reasonable alternative hypothesis for a two-sample t-test?
the two population means are different
When the null hypothesis is rejected in an independent samples t-test, what conclusion is being drawn?
the two populations being compared probably have different means
Which of the following could be a null hypothesis of a two-tailed hypothesis test?
the two populations have the same mean
A two sample t test results in an obtained value for t of zero. When will this happen?
the two samples have the same mean
A two-sample t-test results in an obtained value for t of zero. When will this happen?
the two samples have the same mean
In a histogram or a line graph, what is represented on the x-axis?
the values of a variable
The standard error of the mean best describes
the variability of sample means
Which of these statements is NOT true of a sampling distribution?
the variability of the sampling distribution is the same as the variability of a distribution of individual scores from the same population
Under what circumstances would a score that is 15 points above the mean be considered to be near the center of the distribution?
when the population standard deviation is much larger than 15
When would you expect the standard error of the mean to increase?
when variability in a population is higher
When would you be least likely to need inferential statistics?
when you are only interested in the scores you've measured
The IQR range for a set of scores tells you
where the middle 50% of the scores lie around the median
A doctor collects data from his patients on whether or not they are a smoker. In this example, what are/is the variable(s)?
whether or not someone is a smoker
A doctor collects data from his patients on whether or not they are a smoker. In this example, what is/are the variable(s)?
whether or not someone is a smoker
You just completed a study in which you concluded that female students had significantly higher GPAs than male students. It is possible that
you are making a Type I error
You just completed a study in which you concluded no significant difference in introversion personality scores between greek and non greek students. It is possible that
you are making a type II error
Your scatterplot for two variables shows a circle of points in the lower left part of the graph and one point in the top right of the graph. The best interpretation of this is that
you have no relationship between the two variables but will obtain a positive correlation coefficient as a result of an outlier
If the t value for your independent samples t-test has a p value less than you alpha level, then
you should reject the null hypothesis and conclude that the two group means are significantly different
Which of the following is not a reason why being able to calculate Z-scores is considered important -Z-scores standardize where scores fall relative to the mean -Z-scores change ordinal scales to ratio scales -Z-scores allow scores from different variables or datasets to be directly compared -Z-scores allow specific estimates of relative standing in a population even when information is limited
z-scores change ordinal scales to ratio scales
For a normal population with a SD of 20, what is the z score corresponding to a score that is 10 points below the mean?
z=-.50
Which of the following statements cannot be true for a distribution of scores
60% of the scores are above the mean
Which of the following statements CANNOT be true for a distribution of scores?
60% of the scores are above the median
Positively skewed
- Mode= to the very left -Median= in the middle - Mean > median > mode - Mean= to the right, closest to tail
A set of 30 exam scores with a mean of 60 and a standard deviation of 5 is converted to z-scores. What will be the mean of the transformed scores?
0
Continuous variable
-Allows for fractional amounts -Scale is like a ramp, decimals are possible EX: passage of time, temperature, IQ
For a sample of college students, you measure both the amount of time each day that a person spends on social media and that person's GPA. The scatterplot for these data, with social media time on the x-axis and GPA on the y-axis, indicates a tightly grouped oval of points that is higher on the left side of the graph and lower on the right side of the graph. Your best guess at to the Pearson r correlation coefficient value for these data would be r =
-0.8
Which of the following sets of correlations correctly shows the highest to lowest strength of relationship?
-0.91, +0.83, +0.10, -0.03
Which of the following sets of correlations is correctly ordered from the highest to the lowest degree of relationship?
-0.91, +0.83, +0.10, -0.03
A researcher determines that students study an average of 80+/-20 (M+/-SD or Mean plus or minus Standard Deviation) minutes per week. Assuming these data are normally distributed, what is the z score for students studying 60 minutes per week?
-1
When low scores on one variable occur with high scores on another, and vice versa, their correlation coefficient will be somewhere between ____ and ___
-1 and 0
Any time a researcher conducts a study and uses inferential statistics, it is possible they will
-Commit a type I error -Commit a type II error -Make no error in their conclusions
Dichotomous variable
-Discrete variable that can only have two values EX: pass/fail, living/dying, pregnant/not pregnant
Categorical (discrete) variable
-Measures only whole number amounts -Like a staircase EX: number of cars you own, number of children you have
Negatively skewed
-Mode= to the very right -Median= in the middle -Mean= to the very left, closest to tail -Mode > Median > mean
If the standard error of the mean for a sample is 5 points, then
-The sample may have overestimated the population mean by 5 points -The sample mean may have underestimated the population mean by 5 points
A researcher concludes that a new treatment works significantly better than an existing treatment for improving depression. However, this finding is just unique to the specific sample and does not reflect what would happen in the population. This is an example of...
-Type I error -Incorrectly rejecting the null
A z-score for an x score tells you
-how many standard deviations the score is above or below the mean -whether the x score is above or below the mean -a standardized score that is not dependent on the particular values for the variable measured
Increasing the alpha level (ex: from .01 to .05)
-increases the size of the critical region -increases the probability of a type i error -increases the probability that the sample will fall into the critical region
The probability of a 95% confidence interval including the SAMPLE MEAN is
1
Which set of scores has the least amount of variability
145, 143, 145, 147
Suppose the correlation between heigh and weight for adults is +0.40. What percent of the variability in weight can be explained by the linear relationship between height and weight?
16%
A statistics exam has an average score of 75, with a standard deviation of 4. If a student scores an 83 on the exam, what is their z score?
2
A population of N=10 scores has mean = 50 and standard deviation = 5. What is the population variance?
25
Each quartile of a distribution of scores contains ___ of all the scores
25%
If the variance of a dataset is 16, what is the standard deviation?
4
A set of scores from a sample has a variance of 25, what would the standard deviation be?
5
Identify the median of the following set of scores: 2,2,3,4,5,6,6,9,9
5
A student takes a personality test, which gives them Z-scores for 5 different personality traits, all of which are normally distributed. Their Z-score for extraversion is a -2.0. If the mean extraversion score on the test is a 60 with a standard deviation of 5, what was the student's extraversion score?
50
The range for the scores (4,6,2,8) is what?
6
Variable
A factor that can change in an experiment
If rejecting the null is thought of as a "positive" test result and failing to reject it a "negative", a Type II error could also be called
A false negative
How will a weak positive correlation look on a scatterplot?
A loosely grouped pattern that is lower on the left side of the scatterplot and higher on the right
All other things being equal, in which scenario would the p value for the independent-samples t-test most likely be less than .05?
A mean difference of 6 points and an n (sample size) of 60
A doctor collected data from his patient on whether or not they are a smoker to see how it predicts their health. In this example, whether or not someone is a smoker is
A quasi-independent variable
How will a strong negative correlation look on a scatterplot?
A tightly grouped pattern that is higher on the left side of the scatterplot and lower on the right
A researcher concludes that people who prefer dogs have significantly higher IQ's than those who prefer cats. However, this finding is just unique to the specific sample and does not reflect what would happen in the population. This is an example of...
A type I error
Dr. Stake concludes that morning statistics classes don't differ from afternoon classes in average grade. However, there actually is a difference at the population level. What kind of error has she made?
A type II error
If you scored at the 80th percentile on a test, you would know that -all of the other answers are correct -20% of the students scored higher than you -80% of the students scored lower than you -you scored better than the majority of students who took the test
All of the answers are correct
Which of the following is true of scatterplots?
An inverse (negative) relationship is represented by a slanted line that goes from the upper left corner of the graph down to the bottom corner of the graph
Which statement is true?
As sample size increases, power increases
You decide to create a graph with mean GPA on the y-axis and college classification (freshman, sophomore, junior, senior) on the x-axis. Which of the following would be the most appropriate graph to use?
Bar graph
You decide to record the academic major for each student in an introductory psychology class. If the data are presented in a frequency distribution graph, what type of graph should be used?
Bar graph
What is the biggest advantage of the research design referred to as naturalistic observation?
Behavior is usually more natural
What is the most common way to create a misleading graph?
Change the range of scale units on the y-axis
Variables can be __, but measurements are always __
Continuous, discrete
A researcher counts the number of faculty and the number of students who stop at a stop sign on campus. This is an example of
Descriptive statistics
The owner of a Stove Store wants to calculate what percentage of his ovens that he has sold are range stoves as opposed to another type. This is an example of a
Descriptive statistics
Inferential statistics are used to do what?
Determine whether the patterns between variables are reliable and not due to sampling error
A group of researchers thought that the amount of time alloted to take a quiz would cause changes in students' frustration levels. What was their dependent variable?
Frustration levels
Variability which is defined as difference between third and first quartile is considered as
IQR
Why are inferential statistics so important
Infer something about a population based on data
Which of the following is true about the difference between interval and ration scales?
Interval scales may have a score of 0, but (unlike with ratio scales), it does not represent the true absence of what is measured
Which of these is the correct interpretation of the p value
It shows the probability that you would have obtained the sample statistics value or more extreme if the null were true
What population parameters must be know to run an independent variable the mean of Population 1 the mean of Population 2 the mean and standard deviation of Population 2 none of the above
None of the above
Which of the following is NOT a reason why scatterplots are useful? -Visually displayed data patterns can be easier to understand than numbers alone -Identical correlations can look very different when placed on a scatterplot -Scatterplots can provide information on individual datapoints in addition to the overall relationship between variables -None of the other answers is correct - all are reasons that scatterplots are useful
None of the other answers is correct - all are reasons that scatterplots are useful
Which of the following is true of a normal distribution? -Most individual's scores will be at the low end. -The will be an equal number of low, middle, and high scores. -Most individual's scores will be at the extremes, with few scores in the middle. -None of the other options are correct.
None of the other options are correct
A researcher selects two samples of 25 participants each. In the first sample the population mean was 32 and the variance was 8. In this second sample, the population mean was 4 and the variance was 8. Which sample will be associated with a larger standard error of the mean?
None, both samples will have the same value for SE
A researcher selects two samples of 25 participants each. In the first sample the population mean was 32 and the variance was 8. In the second sample, the population mean was 4 and the variance was 8. Which sample will be associated with a larger standard error of the mean?
None, both samples will have the same value for standard error
Nominal- label or category
Not really on a scale, numbers not comparable. Zero is not a point, just a label. -Type of disorder (schizophrenia) -Religious affiliation -Region of the country -Eye color -Flavor of ice cream -Social security number -Male/female
Ordinal- Rank order
Number used to convey rank order. Numbers are not comparable. Does not have a zero point. -College classification -Grade on a test -Reaction time -Intensity of light -Age classification
Which of the following sample means will have the largest standard error (sampling error)?
One where the sample size is 100 and the population SD is 10
Which of the following is an example of a discrete variable
number of children in a family
A perfect positive correlation would be represented by
Points that form a completely straight line that goes from the bottom left corner of the graph up to the top right corner of the graph
A researcher reports that the size of an effect in Population A is d= 0.10 and the effect size in Population B is d= 0.34. Which population is associated with greater power to detect an effect?
Population B
The average height for women in the US is about 5 ft 4 in. A woman who is 6 ft tall would have a z-score for height that is
Positive
the average height for women in the US is about 5 ft 4 in. A woman who is 6 ft tall would have a z-score for height that is
Positive
A population of scores has a mean of mean = 26, median = 23, and mode = 22. What is the most likely shape for the population distribution?
Positively skewed
Reaction time is a commonly used variable in psychological research. Reaction times are usually close to the minimum possible time but sometimes take considerably longer. Distributions of reaction times are most likely:
Positively skewed
If a person has a z-score of exactly 0, what does that indicate?
The person's score is exactly the same as the mean score
Interval- rank order + equal intervals
Reflects relative amount. Equal intervals between data in set. -Difference between the mean test score and each student's score -Score on the Beck anxiety test (1-44) -Temperature -Weight measured on a scale not calibrated to zero
Which of the following best described a Type I error?
Rejecting a true null hypothesis
Ratio- rank order + equal intervals + absolute zero
Scores reflect the true amount of the variable that is present. Scores measure an amount. Has an absolute/true zero. -Number of college credits completed -Number of correct answers on test -A person's age measured in years -Number of total correct points scored in a season by a sports team
Constant
Stays the same EX: amount of water, sunlight, type of grass used, technique to measure how green the grass is
Which of the following is most likely a continuous variable?
Temperature
Which of the following is an example of a continuous variable?
The amount of time it takes to solve a problem
Suppose a research report indicates that their sample of 100 females had the following statistics regarding IQ scores: M = 110, SE = 1.5. Which of the following is the correct interpretation of these statistics?
The average IQ score for the sample was 110 and that sample mean is most likely off by 1.5 points from the true population mean.
The denominator of an independent-samples t-test represents which of the following?
The difference between the two sample means you can expect to get by chance
The numerator of an independent-samples t-test represents which of the following?
The difference in the two sample means observed in the study
A veterinarian collects information about the weight of her clients' dogs, cats, gerbils, and hamsters. For which group is the standard deviation for weight probably larger?
The dogs
A researcher increases his level of confidence from 90% to 95%. What will happen to the precision of his estimate?
The estimate will be less precise
independent variable
The experimental factor that is manipulated; the variable whose effect is being studied. EX: type of fertilizer
In a frequency distribution graph, the vertical axis shows
The frequency
A recent study reports that students who just finished playing a prosocial video game were more likely to help others than students who had played a neutral game. For this study, what is the dependent variable?
The helping behavior of the students
A recent study reports that students who just finished playing a prosocial video game were more likely to help others than other students who had played a neutral game. For this study, what is the independent variable?
The kind of game given to the students
All other things being equal, which of the following is true?
The larger the absolute value of your test statistic, the smaller your p value
Which of the following is true when you increase the sample size for a study?
The likelihood of rejecting the null increases and there is little to no effect on the effect size
What information can measure of effect size give us that hypothesis testing alone does not?
The magnitude of the difference between populations
The expected value of the sample mean is
The mean of the distribution of sample means
An instructor examines the scores on her first exam, which has typical scale of 1-100 and a fairly normal distribution. Which measure of central tendency is appropriate for this variable?
The mean, median, AND mode
A researcher collects information from all the first year high school teachers in a given city about the subject they teach, their gender, and their age. Which of the following would definitely be a constant (not a variable) in their data?
The number of years they have been teaching
dependent variable
The outcome factor; the variable that may change in response to manipulations of the independent variable. EX: greeness of the grass
If a person has a Z-score of exactly 0, what does this indicate
The person's score is exactly the same as the mean score
If all the possible random samples of size = 30 are selected from a population of scores that is positively skewed with a µ = 80 and a δ = 10 and the mean is computed for each sample, then what shape is expected for the distribution of sample means?
The sample means will form a normal distribution because the sample sizes are relatively large
A new instructional method is found to increase average exam grades from 80.20 to 80.21. That's not much of a change, but it was found to be statistically significant. How could this happen
The sample size was very large
In a frequency distribution graph, the horizontal axis shows
The scores for the variable
If Group 1 in your study has a standard deviation of 10 and Group 2 in your study has a standard deviation of 5, then you know that
The scores in Group 1 are more spread out than the scores in Group 2
Suppose you have a score of 80 on a math exam for which the class average was 70 and the standard deviation 10. Suppose you have a score of 70 on an Spanish exam for which the class average was 50 and the standard deviation 8. For which class did you have the highest score relative to the rest of the students in the class?
The spanish class
The standard error of the sample mean is
The standard deviation of the distribution of sample means
You conduct a study to investigate the possible relationship between number of pets someone has and diastolic blood pressure. The results are as follows: r(70) = -.25, p = .03. Which of the following is the correct interpretation of the results?
The study showed that owning more pets is associated with lower blood pressure.
Dr. Vation tests 50 students' short-term memory. He finds one student has a Z-score of -1.5. What does this tell him about the student's memory?
Their memory is 1.5 standard deviations below the mean memory score
A researcher conducts a study in which one group of students receives encouraging words before a test and a control group receives no encouraging words. She examines the impact of this on test scores. The results are as follows: t(40) = 3.00, p = .004. What is the most appropriate conclusion given an alpha level of .05?
There was a significant difference in test scores between the groups
Which of the following described why confidence intervals are often useful?
They provide a range of estimated values for the population mean rather than a single number
Why are descriptive statistics so important?
Used to describe the important characteristics of data
When is the mode the only measure of central tendency that can be used?
When the variable is nominal or categorical
Based on the effect size conventions, d= 0.60 is a
medium effect size
If there is greater variability of scores in your population, then you would expect
more sampling error
As the SE of the mean goes up, individual means will be
more spread out among the population mean
To get a more precise estimate of a population parameter from a confidence interval, you would need a ___ interval, providing ____ confidence.
narrow, weaker
A researcher records the odometer reading and price for a group of used Hondas. What kind of correlation is likely to be obtained for these two variables?
negative
If high scores on one variable are associated with low scores on another variable, this indicates a
negative correlation
What type of scale of measurement doesn't involve measuring a quantity?
nominal
Measures of effect size are important statistics because
null hypothesis testing only allows you to conclude whether or not there is a significant effect- not how large the effect is
A null hypothesis is most likely to be rejected when
the effect size is large, but there is little variability in the scores
What is the main difference between an independent samples t-test and a single sample t test?
the independent samples test uses sample means to estimate both population means
What is the main difference between an independent samples t-test and a single sample t-test?
the independent samples test uses sample means to estimate both population means
quasi-independent variable
the independent variable that is used to create the different groups of scores EX: males and females
The correct interpretation of a 95% confidence interval is that
the interval has a 95% chance of including the population mean
The higher the confidence interval (e.g., 95% vs 90%)
the larger the range of values as estimates of the population
The weights of male and female students in a class are summarized in the boxplots below. Which of the following statements is NOT true?
the male students' weights have less variability than the female students' weights
The weight of male and female students in a class are summarized in the boxplots below. Which of the following statements is not true?
the males students' weights have less variability than the female students' weights
What are confidence intervals most often used to estimate
the mean of a population
The midpoint of a confidence interval is always
the mean of the sample (single sample study) or the mean difference in the samples (two-group study)
A sample of n = 25 individuals is selected from a population with mean = 80 and a treatment is administered to the sample. If the treatment has no effect, then
the sample mean should be close to 80 and should lead you to fail to reject (retain) the null hypothesis
f all the possible random samples of size = 10 are selected from a population of scores that is normally distributed with a µ = 80 and a δ = 10 and the mean is computed for each sample, then what shape is expected for the distribution of sample means?
the sample means will form a normal distribution because the parent population is normal
A z score of 3 or higher indicates
the score is far from the mean
All other things being equal, the larger your sample size (n)...
the smaller the standard error of the mean
The standard error of the sample mean is
the standard deviation of the distribution of sample means
Cohen's d measures effect size in what units?
the standard deviation of the variable
As the sample size becomes very large
the standard error becomes very small
What happens to the standard error of the mean when the sample size increases
the standard error decreases
When a random sample is selected from a population, the sample mean is not expected to be exactly equal to the population mean. On average, the size of the difference between the sample mean and the population mean is predicted by
the standard error of the mean
Which of the following defines the expected difference between a population's mean and the mean of a sample randomly drawn from it
the standard error of the mean
Which of the following defines the expected difference between a population's mean and the mean of a sample randomly drawn from it?
the standard error of the mean
The statistical output for an independent samples t-test shows t(32) = 1.26, p= .50. This output indicates that
the study has 34 participants and you should conclude that the two groups are NOT significantly different
For a sample of college students, you measure both the amount of time each day that a person spends on social media and that person's GPA. The scatterplot for these data, with social media time on the x-axis and GPA on the y-axis, indicates a tightly grouped oval of points that is higher on the left side of the graph and lower on the right side of the graph. Your interpretation of this scatterplot would be
there is a strong negative correlation between social media time and GPA
For an independent samples t-test, the null hypothesis states that
there is no difference between the two population means
The null hypothesis for a one-sample test states
there is no difference between the two population means
Suppose a researcher collects the degrees in Celcius and Farenheit in Conway over a month. Which of the following statements is most correct?
there would be a perfect positive correlation
You conduct a study to investigate the possible relationship between the number of bystanders around a victim that needs help and the time it takes for someone to provide help. The result of your Pearson correlation coefficient analysis showed r (46) = +0.15, p = +0.08. The most appropriate conclusion would be that
this study showed no significant relationship between the number of bystanders and time to provide help
Which statistic does not belong with the others? -range -mean -SD -variance
variance
If you choose a sample at random from a population, it will most likely be
very close to the population mean
In which of the following scenarios would the assumption of homogeneity of variance be violated
when one group has a narrow distribution of scores and the other group has a very wide distribution of scores
Field research
▪ A qualitative method of data collection that aims to observe, interact, and understand people while they are in a natural environment
Correlational study
▪ Correlation is not causation ▪ Relationship questions ▪ Measure variables and see if those variables are related to one another ▪ Ex: Bob eats pizza with fungus and starts having hallucinations ▪ Correlations predict the possibility of cause-and-effect relationships, but they cannot prove them
Survey research
▪ Great way to access people's consciously held attitudes and beliefs ▪ Subtle word choices can influence results ▪ Who you ask always needs to be taken into account ▪ Random sample should be taken
Laboratory research
▪ May use special equipment and cells or animals to find out if a drug, procedure, or treatment is likely to be useful to humans
naturalistic observation
▪ Researchers watching behavior in a natural environment ▪ Let the subjects just do their thing without trying to control the situation ▪ Great at describing behavior but they're very limited at explaining it
Case study
▪ Take an in depth look on one individual ▪ Memorable ▪ Run the risk of overgeneralizing
Mode
▪ The most frequently occurring score. Score with the highest frequency. ▪ Unimodal- has only one major peak ▪ Bimodal- has two major peaks. Ex: sample taken 2x in one day ▪ Most commonly used with nominal data ▪ Arrange the scores in ascending order from lowest to highest to figure out mode ▪ Advantages ● Ignores much of the data, quick and easy way to measure for ordinal and scale variables ▪ Disadvantages ● Ignores much of the data, does not consider scores other than the most frequent
Median
▪ The score at the center of the data ▪ Put data in ascending order, find number in the middle of the data ▪ Prefer when the data are ordinal ▪ Advantages ● Can only have one score (be one number) ● Can be useful with highly skewed data ▪ Disadvantages ● Will not always be one of the scores in the actual data set ● Not useful with nominal data ▪ USE THIS IF OUR DATA IS SKEWED A LOT
Mean
▪ The score located at the mathematical center of the distribution ▪ AKA the average ▪ Usually measures interval data ▪ Add up all scores and divide by total ▪ Advantages ● Only used with interval or ratio level data not excessively skewed ● May be useful for planning ● Relatively stable and can be used for analysis ▪ Disadvantages ● May not actually exist in the sample ● Most susceptible to outliers ● Variables must be scale level and not highly skewed
Experimental study
▪ allow investigators to isolate different effects by manipulating an independent variable and keeping other variables constant ▪ Experimental- going to get messed with ▪ Control group- not going to get messed with ▪ Not always being informed about what is being tested
When should a frequency distribution be graphed as a bar graph or bar chart?
○ Each column represents a discrete (categorical) variable. ○ Used to COMPARE the frequency for a category or characteristic with another category or characteristic. ○ Ex: country of birth
What does a frequency distribution tell you
○ Frequency distributions are essentially graphs, diagrams, or figures that present data in a more organized, readable way. ○ It can show data as RELATIVE or ABSOLUTE. Ex: proportions or percentages
When should a frequency distribution be graphed as a histogram (or line graph called a frequency polygon)?
○ In a histogram, a column represents a numeric variable that is continuous or grouped ○ The height of a column shows the frequency for specific range of values ○ Show the distribution of all observations in a qualitative set (has numbers) ○ Ex: Height of children
What is a stem and leaf plot and what does it show?
○ The leading values become the stems and the trailing values the leaves ○ Gives a good idea about the distribution of numbers ○ Presents qualitative data in graphical format
Which of the following is more likely a variable measured on a ratio scale?
minutes to complete a race
A population of scores has a mean = 22, median= 23, and mode= 26. What is the most likely shape for the population distribution?
negatively skewed
On a particularly easy general psych exam, most students got As and nearly everyone else got Bs. There were, of course, a few Cs and even fewer Ds and Fs. The shape of the distribution of scores could be described as
negatively skewed
Whether or not someone is married represents which scale of measurement?
nominal
Which of the following is an example of a discrete variable?
number of stoplights in a city
An example of a variable measured on a nominal scale is
number on an athletic jersey
Which of the following research situations would be most likely to use a quasi-experimental design with different people in different groups?
Compare the mathematic skills for the 9th grade boys versus 9th grade girls
A researcher records if each participant is a parent or not. Which of the following is a level?
-Being a parent -Not being a parent
Which of the following is true
-Inferential statistics often involve first calculating descriptive statistics -Descriptive statistics can be preformed without inferential statistics
Why do many researchers prefer the experimental methods of research?
-The experimental method allows researchers to control for extraneous variables -This method can provide a cause/effect relationship between variables
Why do many researchers prefer the experimental method of research?
-The experimental methods allows researchers to control for extraneous variables -This method can both provide a cause/effect relationship between variables
What is the advantage of correlational research designs?
-They often do not require a controlled lab environment -They allow you to do research on variables that you cannot or should not manipulate -They allow you to assess the relationships between variables
What is the mode for the following set of scores: 3,3,1,5,8,7,6,9
3
A population of N=8 scores has EX=40. What is the population mean?
5
What disadvantage does a lab study have compared to a field study?
Behavior may be less realistic
A statistics instructor pulls out 10 of her students' exams from a pile of 50 to start grading. Because the suspense is killing her, she calculates the mean exam score for these 10 students to get a better idea of how they might do. The instructor has used
Both descriptive and inferential statistics
Which of the following is true of a normal distribution? Most individual's scores will be at the low end. The will be an equal number of low, middle, and high scores. Most individual's scores will be at the extremes, with few scores in the middle. None of the other options are correct.
None of the other options are correct
A researcher is interested in the impact of natural surroundings on brainstorming. She randomly assigns some individuals to brainstorm as many uses of a brick as they can imagine while sitting in a garden and others to do the same brainstorming task while sitting in a cubicle. The independent variable is
The location of the brainstorming task
A researcher believes that powdered unicorn horn improves memory. To test this, the researcher has participants study a list of 20 words. Prior to this, the researcher sprinkles half of the participants on the head with powdered unicorn horn and the other half with baby powder. What is the independent variable in this study?
The type of powder
A histogram would be used instead of a bar graph if ___
The variable is continuous
If the same data is displayed in a frequency polygon (line graph) and a bar graph, how will the shapes of the two graphs differ?
There will be no difference in shape
When is the mean considered least useful as a measure of central tendency?
When the distribution is very skewed or contains extreme outliers
When would you be the least likely to need inferential statistics?
When you are only interested in the scores you've measured
Professor Sample wants to know if people's age is related to their short-term memory. This question is best answered by:
a correlational study
For a research study comparing attitude scores for males and females, participant gender is an example of what kind of variable?
a quasi-independent variable
Dependent variables
are measured for possible changes
If a researcher tests a hypothesis on a sample of individuals, the researcher will almost certainly need
both descriptive and inferential statistics
If a researcher wants to use data from a sample to draw conclusions about a population, they would need to use
both descriptive and inferential statistics
An advantage of experimental research over correlational research is
clearer statements of causality can be made
A good example of descriptive statistics would be when you
create a bar graph that shows student average course evaluations for male and female instructors
A researcher calculates the average reaction time for a visual stimulus and for an auditory stimulus. This is an example of
descriptive statistics
The owners of Cupid's Stupid Divorce Attorney's discover that they have won 0% of all their clients cases. This is an example of
descriptive statistics
Many majors (like psychology) have "category requirements" for elective classes. For example, Theories of Learning (PSYC 3351) and Cognitive Psychology (PSYC 3325) are labeled "Category II." Health Psychology (PSYC 3305) and Sports Psychology (PSYC 3370) are labeled "Category IV". The category to which a course belongs is what type of variable?
discrete, qualitative
Cause/effect questions are the type of questions used by which method of research
experimental
Cause/effect questions are the type of questions used by which method of research?
experimental
A list of all possible values of a variable and the number of times each value occurs is called a
frequency distribution
Which of the following variables would most likely result in a positively skewed distribution of scores?
home prices in LR, AR
A frequency distribution shows
how many individuals scored a particular score for a variable that you measured
The term "inferential" in inferential statistics is appropriate because we
infer about the characteristics of a population based only on a sample
Most often, when you arrive at a conclusion about your study's hypothesis, the last step in the statistics requires
inferential statistics
Testing hypotheses is generally done through some form of
inferential statistics
What term is used to denote statistical procedures that use sample data to make conclusions about the larger population from which the sample was obtained?
inferential statistics
What scale of measurement are most psychological variables (ex: depression, anxiety, mood, attitude) assumed to follow?
interval
What scale of measurement is used for quantitative variables, but has an arbitrary zero point?
interval
