Psych Stats - Test #1
R-squared as a measure of effect size will always have a value in the range _________ and indicates the ________.
0-1; proportion of variance accounted for
Which set of scores has the least amount of variability?
145, 143, 145, 147
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%
A set of scores from a sample has a variance of 25, what would the standard deviation be?
5
Which of the following statements CANNOT be true for a distribution of scores?
60% of the scores are above the median.
Which of the following research situations would be most likely to use a quasi-experimental design with different people in different groups?
Compare the mathematics skills for 9th-grade boys versus 9th-grade girls
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
What kind of distribution shape can NOT be symmetrical?
Skewed
What is the advantage of correlational research designs?
They often do not require a controlled labratory 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.
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 owners of Cupid's Stupid Divorce Attorneys discover that they have won 0% of all their client's cases. This is an example of a
descriptive statistic
Cause/effect questions are the type of questions used by which method of research?
experimental
Most often, when you arrive at a conclusion about your study's hypothesis, the last step in the statistical analysis requires
inferential statistics
What scale of measurement are most psychological variables (e.g., depression, anxiety, mood, attitude) that use a Likert scale (e.g., 1-5, 0-10, etc.) to measure the psychological variable assumed to follow?
interval
Which statistic does not belong with the others?
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
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
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
As the standard error of the mean goes up, individual means will be
More spread out aroung the population mean
The probability of a 95% confidence interval including the SAMPLE MEAN is
1
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
If the standard deviation of a dataset is 9, what is the variance?
81
Which set of scores has the least variability?
91, 92, 93, 94
What disadvantage does a lab study have compared to a field study?
Behavior may be less realistic
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
Dr. Stake concludes that students who study more get higher average statistics grades than students who study less, and there actually is a difference at the population level. What kind of error has she made?
No error has been made
What type of scale of measurement doesn't involve measuring a quantity?
Nominal
Bar graphs are used to represent the frequency for which type of variables?
Nominal and Ordinal
Which of the following is true of a normal distribution?
None of the other options are correct.
The numerator of an independent-samples t-test represents which of the following?
The difference in the two sample means observed in the study.
Inferential statistics are estimates of unknown information, so they always involve some degree of _________
Uncertainty
An independent samples t-test is appropriate for what type of research design?
a between-participants design
Other things held constant, as you increase sample size, the shape of the sampling distribution of the mean will
decrease
A list of all possible values of a variable and the number of times each value occurs is called a
frequency distribution
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
For a perfectly symmetrical normal distribution, which relationship is always true?
mean = median = mode
The course numbers for 2000-level courses (for example, MATH 2331, PSYC 2330, or PSYC 2370) are examples of which scale of measurement?
nominal
An example of a variable measured on a ratio scale is
number of random acts of kindness observed
An example of a variable measured on a nominal scale is
number on an athletic jersey
The standard deviation for the distribution of sample means is called the
standard error
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 standard error of the mean best describes
the variability of sample means
For a normal population with a standard deviation of 20, what is the z-score corresponding to a score that is 10 points below the mean?
z=-0.50
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
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
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
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
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
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 psychology major?
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 selecting a score that is between 1 standard deviation below and 1 standard deviation above the mean would be
0.6826
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 standard deviation of the transformed scores?
1
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
An introductory psychology class has 9 freshman males, 15 freshman females, 8 sophomore males, and 12 sophomore females. What is the probability of randomly selecting a male from this class?
17/44
If you scored at the 80th percentile on a test, you would know that
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
If the variance of a dataset is 16, what is the standard deviation?
4
A population of N = 8 scores has EX = 40. What is the population mean?
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
What is the median for the following set of score: 1, 3, 3, 5, 6, 7, 8, 9, 10
6
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
A good analogy for a type II error is...
A blood test incorrectly indicating that a person does not have Lycanthropy
A good analogy for a type I error is...
A blood test incorrectly indicating that a person has Lycanthropy
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.
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
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
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
What is a sample mean often treated as an estimate of?
A population mean
A doctor collect data from his patients 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
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
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...
A type I error incorrectly rejecting the null A type 2 error A&B are correct
What is the biggest advantage of the research design referred to as naturalistic observation?
Behavior is usually more natural
Which of the following is true?
Descriptive statistics can be performed without inferential statistics Inferential statistics often involve first calculating descriptive statistics
Inferential statistics are used to do what?
Determine whether the patterns between variables are reliable and not due to sampling error
______ 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
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
What is one way to decrease the standard error of the mean?
Increase the sample size
Which of the following is true about the difference between interval and ratio 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 statistic's value or more extreme if the null were true
A researcher reports that the size of an effect in some population is d = 0.88. Which of the following is an appropriate interpretation for d?
Mean scores shifted 0.88 standard deviations in the population.
The measure of central tendency that is the same as the 50th percentile is the
Median
Suppose a class takes a quiz and the majority of scores are high with fewer low scores. Which is the most likely shape of the distribution?
Negatively Skewed
Whether or not someone is in the experimental group or the control group in a study represents which scale of measurement?
Nominal
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 standard error
Which of the following sample means will have the largest standard error (sampling error)?
One where the sample size is 100 and the population standard deviation is 10
A person's class rank amongst their high school class is an example of which scale of measurement?
Ordinal
Determining the class standing (1st, 2nd, and so on) for the graduating seniors at a high school would involve measurement on a(n) _____ 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
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
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
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?
Postively skewed
An instructor randomly assigns some of her classes to engage in a 3 minute mindfulness breathing activity before a quiz and others classes to engage in a 3 minute break before a quiz. She compares their quiz scores to see which group performed better. What is the dependent variable?
Quiz scores
Many physical dimensions such as height, depth and distance are _________ variables
Ratio
The number of pets a person has represents which scale of measurement?
Ratio
Which of the following best describes a Type I error?
Rejecting a true null hypothesis
Which of the following is most likely a continuous variable?
Temperature in degrees Celsius
Inferential statistics are most commonly used to do what?
Test a hypothesis
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 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.
A veterinarian collects information about the weight of her clients' dogs, cats, gerbils, and hampsters. 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
Why do many researchers prefer the experimental method of research?
The experimental method allows researchers to control for extraneous variables This method can provide a cause/effect relationship between variables
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 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 (e.g., sample size, etc), 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
A researcher is interested in the impact of natural surroundings on brainstorming. She randomly assigns some invidviduals 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
What information can measures of effect size give us that hypothesis testing alone does not?
The magnitude of the difference between populations
Which of the following is an example of a descriptive statistic?
The mean of a sample of test scores
A set of students is surveyed about their major, what is the best measure of central tendency for this variable?
The mode
An instructor examines the scores on her first exam, which has a typical scale of 1 to 100 and a fairly normal distribution. Which measure of central tendency is appropriate for this variable.
The mode The median The mean
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
What would be a reasonable null hypothesis for a two-sample t-test?
The population means are the same.
The power of a statistical test is best described as the
The power of a statistical test is best described as the
If the standard error of the mean (SE) 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
If 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
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 that 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.
The standard error of the sample mean is
The standard deviation of the distribution of sample means.
A histogram would be used instead of a bar graph if ________
The variable is continuous
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 score 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 is a continuous variable?
Weight
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.
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.
When is a bar graph more appropriate to use than a histogram?
When scores are discrete
When is the mode the only measure of central tendency that can be used?
When the variable is nominal or categorical
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
Under what circumstances is the median likely to produce a better measure of central tendency than the mean??
With an extremely skewed distribution
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 of the following is NOT a reason why being able to calculate Z-scores is considered important?
Z-scores change ordinal scales to ratio scales
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
A z-score of z = 2.00 indicates a position in a distribution
above the mean by a distance equal to 2 standard deviations
Any time a researcher conducts a study and uses inferential statistics, it is possible they will
all of the above are true
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 test is NOT true?
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
A hypothesis test is
an inferential technique that uses the data from a sample to draw inferences about a population
Which of the following is an example of a continuous variable?
annual rainfall in a town
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
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 the whole class might do. The instructor has used
both descriptive and inferential statistics
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 example of a variable measured on an ordinal scale is
college classification (freshman, sophomore, etc.)
Variables can be __________, but measurements are always __________
continuous, discrete
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
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
What term is used to denote statistics that are only derived from the individuals in the study and not from the larger group of individuals that you, as the researcher, is interested in?
descriptive statistic
A researcher calculates the average reaction time (in milliseconds) for a visual stimulus and for an auditory stimulus. This is an example of
descriptive statistics
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 becasue 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
Why are deviation scores not useful measures of variability in a sample?
deviation scores across a sample will always add up to 0
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
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
You decide to create a graph with mean GPA on the y-axis and number of hours studied per week on the x-axis. Which of the following would be the most appropriate graph to use?
either a histogram or frequency polygon
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
Which of the following would be appropriate for depicting the distribution of heights for people enrolled in this class?
histogram
Which of the following variables would most likely result in a positively skewed distribution of scores?
home prices in Little Rock, AR
When reporting household incomes for a geographical region (i.e., city, state, nation), the median is preferred over the mean. This is because
household incomes likely represent a skewed distribution
A frequency distribution shows
how many individuals scored a particular score for a variable that you measured
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 (for example 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 all of the above are true
The term "inferential" in inferential statistics 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
Testing hypotheses is generally done through some form of __________
inferential statistics
Variability which is defined as difference between third and first quartile is considered as
interquartile range
What scale of measurement is used for quantitative variables, but has an arbitrary zero point?
interval
Based on the effect size conventions, d = 0.60 is a
medium effect size
Which of the following is most likely a variable measured on a ratio scale?
minutes to complete a race
If there is greater variability of scores in your population, then you would expect
more sampling error
To get a more precise estimate of a population parameter from a confidence interval, you would need a _________ interval, providing _________ confidence.
narrow, weaker
On a particularly easy general psychology 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
What is the shape of the distribution for the following set of data? Scores: 1, 2, 3, 3, 4, 4, 4 5, 5, 5, 5, 6, 6, 6, 6, 6, 7
negatively skewed
Whether or not someone is married represents which scale of measurement?
nominal
Measures of effet 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
Conceptually, the standard error of the mean tells you
on average, how far off your samples means are likely to be from the true population mean
Using inferential statistics to arrive at 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 statistics instructor calculates the standard deviation (how different scores are from each other) for a set of homework scores to see how much scores tend to differ. The instructor has used
only descriptive statistics
A person's class rank amongst their high school class represents which scale of measurement?
ordinal
As 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
The most powerful way to create the groups for an independent samples t-test is to
randomly assign participants to two different groups
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 draw inferences about the characteristics of a __________
sample:populaition
In a normal distribution, what scores have the highest probability of being randomly drawn?
scores that are closer to the mean
Based on the effect size conventions, d = 0.18 is a
small effect size
On an exam with a normal distribution and a population mean of 30, you have a score of 35. Which value for the standard deviation would give you the highest position in the class distribution?
standard deviation = 2
The standard error of the mean (SE) is like the
standard deviation for the sampling distribution of means
A number that describes how likely your sample mean will be close to the true population mean is the
standard error of the mean
The best measure of sampling error is the
standard error of the mean
What do descriptive statistics allow us to do?
summarize the characteristics of a sample of scores
The purpose of descriptive statistics is to
summarize the data that has been collected
Which of the following is NOT a measure of effect size?
t score
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
If a researcher conducts both a one-tailed and two-tailed hypothesis test, both with an alpha of .05, which is true of the two tests' critical regions?
the critical region is the same size in both tests
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 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 describes the most appropriate conclusion to take from the test:
the effect is likely but not certain to exist in the population
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
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 higher that a score is in a distribution of scores
the lower the probability of randomly selecting such a score
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
What is 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 therapist is investigating the impact of a new treatment for depression compared to an old treatment. Which of the following accurately representes 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 representes the null hypothesis.
the new treatment produces results that are the 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
If each sample includes only 1 score, the standard error of the sample means would be
the population standard deviation
The alpha level determines
the probability of a Type I error
For a normal distribution with mean = 60 and standard deviaton = 8, the probability of selecting a score greater than X = 64 is equal to
the proportion of the distribution with z-scores greater than 0.50
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 80 and should lead you to fail to reject (retain) the null hypothesis
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
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
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
The statistical output for an independent samples t-test shows t(32) = 1.26, p = .50. This output indicates that
the study had 34 participants and you should conclude that the two groups are NOT significantly different
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
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
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
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
The null hypothesis for a one-sample test states
there is no difference between the two population means
Which of the following describes why confidence intervals are often useful?
they provide a range of estimated values for the population mean rather than a single number
Which of the following is an example of a discrete variable?
time to complete a test
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
When we use inferential statistics to arrive at a conclusion in our study
we are confident of our conclusion but realize that we are not 100% sure
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 interquartile range for a set of scores tells you
where the middle 50% of the scores lie around the median
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