PSY 138 FINAL
A researcher is interested in whether the color of an animal's surroundings affects learning rate. She tests 16 rats in a box with colorful wallpaper. It is known that the average rat of this strain can learn to run this particular type of maze in a box without any special coloring in 25 trials, with a variance of 64; the distribution is normal. The mean number of trials to learn the maze for the rats tested with the colorful wallpaper is 11. What is standard error?
(sqrt 64)/(sqrt 16) = 2.00.
A jar contains 10 red marbles and 20 blue marbles. A random sample of n = 3 marbles is selected from the jar. Assuming sampling with replacement, if the first two marbles are both blue, what is the probability that the third marble will be red
10/30
What is the value of SS for the following set of scores? Scores: 5, 6, 1
14
If the standard deviation is 4, what is the variance?
16
An introductory psychology class has 9 freshman males, 15 freshman females, 8 sophomore males, and 12 sophomore females. A random sample of n = 2 students is selected from the class. Assume that sampling with replacement is used. If the first student in the sample is a male, what is the probability that the second student will also be a male
17/44
A sample of n = 4 difference scores produces SS = 48. What is the estimated standard error for the sample mean difference?
2 SD/SQRT of N
You randomly select someone from a group of 12. Two of those in the group were born in Iowa. What is the chance you will pick a person born in Iowa?
2/12= .17
A sample of n = 5 scores produces SS = 20. The variance for this sample is ___
20/4= 5
A distribution with µ = 35 and σ = 8 is being standardized so that the new mean and standard deviation will be µ = 50 and σ = 10. In the new, standardized distribution your score is X = 60. What was your score in the original distribution?
35+8= 43
A population has µ = 40 and σ = 8. If each score is divided by 2, the new standard deviation will be _____
4
A sample of n = 5 scores has SS = 40. If the same five scores were a population, then the value obtained for the population SS would be _____.
40
A sample of n = 5 scores has a mean of M = 45 and a variance of s2 = 20. Using this sample, the 90% confidence interval for the population mean is
45 ± 2.132(2)
One sample has n = 8 and SS = 21 and a second sample has n = 8 and SS = 35. What is the pooled variance for the two samples?
56/16
A sample has SS = 20 and s2 = 4. How many scores are in the sample
6
The sum of the squared deviation scores is SS = 60 for a population of N = 5 scores. What is the variance for this population?
60/5=12
A professor recorded 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
A bar graph
In a hypothesis test using a t statistic, what is the influence of using a larger sample
A larger sample tends to increase the likelihood of rejecting the null hypothesis.
A repeated-measures study would not be appropriate for which of the following situa-tions? A. A researcher would like to study the effect of practice on performance. B. A researcher would like to compare individuals from two different populations. C. The effect of a treatment is studied in a small group of individuals with a rare disease. D. A developmental psychologist examines how behavior unfolds by observing the same group of children at different ages
A researcher would like to compare individuals from two different populations
In principal, you could make a distribution of sample means by
A. calculating the mean of all the possible samples of a given size and dividing it by the variance.
If finding average age of freshmen at ISU, you ask the first 100 freshman you meet how old they are. What is the population?
All freshman at ISU
You have a score of X = 65 on an exam. Which set of parameters would give you the best grade on the exam? A. μ = 60 and σ = 10 B. μ = 60 and σ = 5 C. μ = 70 and σ = 10 D. μ = 70 and σ = 5
B. M=60 and SD=5
Which of the following is true about making a scatterplot? A. The values on the vertical axis go from highest at the bottom to lowest at the top. B. The overall shape should be roughly square. C. You always mark two dots for each score. D. All of the above.
B. The overall shape would be roughly square
Which of the following is a fundamental difference between the one sample t test and a 1 sample z-test? A. The t statistic uses the sample mean in place of the population mean. B. The t statistic uses the sample variance in place of the population variance C. The t statistic computes the standard error by dividing the standard deviation by n - 1 instead of dividing by n. D. All of the above are differences between t and z
B. The t statistic uses the sample variance in place of the population variance
A distribution is positively skewed. Which is the most probable order for the three measures of central tendency? A. mean = 40, median = 50, mode = 60 B. mean = 60, median = 50, mode = 40 C. mean = 40, median = 60, mode = 50 D. mean = 50, median = 50, mode = 50
B. mean = 60, median = 50, mode = 40
Not an example of an interval scale: A. measure of temperature in Fahrenheit B. measure of temperature in Celsius C. measuring the time it takes to run 100 yards D. A measure of an individual's shyness
C. Measuring the time it takes to run 100 yards
Several samples, each with n = 9 scores, are selected from a population. If the t statistic and the z-score are computed for each sample mean, which of the following is probably true?
C. The set of t statistics will be more variable that the set of z-scores
How do you decide whether to reject the null hypothesis
Compare the Z score needed to reject the null hypothesis to the actual Z score of the sample
The mean score on a creativity test is 20 and the standard deviation is 5. The distribution is considered to be normal. Using the percentage approximations for normal curves, how many people would get a score between 15 and 25?
D. 34% + 34% = 68% find z and look up %
What is not true about ordinal measures? A. Their distribution is always rectangular B. the exact degree of difference between scores does not have meaning beyond one being higher than the other C. They're also called rank-order measurements D. Categories are ranked according to frequency of scores in different categories
D. Categories are ranked according to frequency of scores in different categories.
Which is not a continuous variable? Why? A. Time it takes to solve a problem B. Temperature C. Height D. number of children
D. Number of children. It cannot be broken down into smaller chunks.
An ordinal scale of measurement lacks which one of the following properties of a scale? A. equal orders B. unequal orders C. equal intervals D. unequal intervals
D. Unequal intervals
A psychologist is interested in studying aggressive tendencies in people and develops a measure of this personality characteristic. What kind of statistic is the characteristic of aggression?
Descriptive Statistic
Statistical techniques that summarize, organize, and simplify data
Descriptive Statistics
What is a correct argument for using a two-tailed test even if there is a clear basis for predicting a result in a given direction
If an unexpected result comes out opposite to what is predicted, it does not have to be ignored.
_____ allow you to make statements that the results would happen if you were to conduct an experiment a number of times with multiple samples.
Inferential Statistics
Leticia has collected data on the relationship between physical attractiveness and judgments of personality characteristics. In order to determine if the results obtained from the sample are representative of the population, Leticia will need to employ _____
Inferential statistics
What scale(s) should be used to determine the size of the difference between two measurements
Interval or Ratio scale
What is a correct argument for using a one-tailed test when there is a clear basis for predicting a result in a given direction
It's less conservative so it is easier to reject the null hypothesis
A sample is selected from a population with μ = 80, and a treatment is administered to the sample. If the sample variance is s2 = 20, which set of sample characteristics is most likely to lead to a decision that there is a significant treatment effect (reject H0)? A. M = 85 for a sample of n = 25 B. M = 85 for a sample of n = 100 C. M = 90 for a sample of n = 25 D. M = 90 for a sample of n = 100
M = 90 for a sample of n = 100
Researchers have identified style of leadership as relationship or task-oriented
Nominal Scale
the specific method used to measure or manipulate a variable
Operational Definition
Measures physical dimensions like number of items correct, amount of alcohol consumed, and time taken to respond
Ratio Scale
Difference between interval and ratio scale is
Ratio scales have an absolute 0 point, and Interval scales do not.
YOU HAVE JUST RECEIVED A NEW TAPE MEASURE. WHEN YOU MEASURE THE SAME BOARD 4 TIMES, YOU FIND MEASUREMENTS FLUCTUATE FROM 4-8 IN. THE NEW TAPE MEASURE IS LOW IN _________
Reliability
Your car speedometer fluctuates between 15 & 90 mph while going a constant speed. Your speedometer is low in _______
Reliability
do we get the same score with repeated measures
Reliability
sample variance (s^2)
SS/(n-1)
Random assignment of half of the participants to group one and the other half to group two is an example of
Simple Random Assignment
SS equation
Sum of (X-mean)^2
The null hypothesis for a repeated-measures test states:
The entire population will have a mean difference of μD = 0.
A social psychologist interested in relationships has developed a scale that measures the degree of affection adult men feel for their father. She found that for the general population the distribution is skewed to the right, the mean degree of affection is 60, and the standard deviation is 16. She now is wondering if men who have themselves just become new fathers will score higher on the scale than men in general. She samples a group of 100 new fathers and finds that their mean is 64.5. What is the research hypothesis?
The population of new fathers has a higher mean than the mean of the population of men in general
A researcher obtains a value of -8.50 for a chi-square statistic. What can you conclude because the value is negative?
The researcher made a mistake. chi-square statistic cannot be negative
A researcher tests whether there is any difference between how fast people work in the morning versus how fast they work in the evening. What is the null hypothesis?
There is no difference in the speed at which people work.
Failing to reject the null hypothesis when the research hypothesis is true is referred to as
Type 1 error
Setting the significance level at a very high cutoff (such as 20%) increases the chances of
Type 1 error
Failing to reject the null hypothesis when the research hypothesis is true is referred to as
Type II error
Our student: Final exam score = 85; Class: M = 70; SD = 10. His friend: Final exam score = 45; Class: M = 35; SD = 5. Compute the Z score for our statistics student and his friend.
Z= (X-mean)/population standard deviation Our student, Z = 1.50; his friend, Z = 2.00
Before conducting inferential statistics, Tim selects the probability level required for statistical significance. This level is referred to as the _____ of the test
alpha level
In general, an increase in variance for the sample of difference scores will cause ______
an increase in the standard error and a decrease in the value of t
Dr. King asks student teachers to assign a punishment for misbehavior displayed by attractive vs. unattractive students. What is the response variable? (Dependent Variable)
assigned punishment
For a negatively skewed distribution with a mode of X = 25 and a mean of M = 20, the median is probably
between 20 and 25
One sample of n = 5 scores has a variance of s2 = 10 and a second sample of n = 10 scores has s2 = 20. If the pooled variance is computed for these two samples, then the value obtained will be ______.
closer to 20 than 10
The variance of a distribution of sample means of more than one is
greater than the original population variance
A professor recorded scores from a 5-point quiz 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
histogram
What kind of frequency distribution graph is appropriate for scores measured on an interval or ratio scale
histogram or line graph
Using the .05 level of significance means that A. in the long run, 1 time in 20 you will have a Type I error. B. it is easier to reject the null hypothesis than if you used a .10 significance level. C. there must be a very large effect size in order for there to be a significant result, regardless of the number of participants. D. the experimental group is expected to be further away from the mean of the population than if a .10 significance level were used.
in the long run, 1 time in 20 you will have a Type I error.
Assuming that other factors are held constant, which of the following would tend to decrease the value of the t statistic (make it closer to zero)?
increase sample variance
When there is no linear correlation, the correlation coefficient
is 0
Which set of sample characteristics is most likely to produce a significant value for the independent-measures t statistic
large mean difference and small sample variance
Which combination of factors has the greatest likelihood of rejecting the null hypothesis?
large sample and small variance
Which combination of factors would definitely reduce the width of a confidence interval
larger sample and decrease level of confidence
smaller t value
larger sample and smaller sample variance
For a negatively skewed distribution with a mode of X = 25 and a median of 20, the mean is probably _____
less than 20
Results are generally said to be statistically significant when there is a ________ probability of the results occurring if the population means are actually equal
low
A repeated-measures experiment and a matched-subjects experiment both produce t statistics with df = 20. Which experiment used more subjects?
matched design (df= n-2)
The most common single number in a group of scores is the
mode
The median is greater than the mean in a distribution that is
negatively skewed
A normal distribution has μ = 100 and σ = 20. What is the probability of randomly selecting a score less than 130 from this distribution
p = .0668
Inferential statistics allow us to arrive at conclusions about the _____ on the basis of _____ data.
population; sample
What is the shape of the distribution for the following set of data? Scores: 1, 2, 2, 2, 2, 3, 3, 4, 5, 6
positively skewed
Which set of sample characteristics is most likely to produce a large value for the estimated standard error
small sample large variance
The data from a repeated-measures research study show that all of the subjects scored about 10 points higher in treatment I than in treatment II. These data will produce
small sample variance and large t statistic
The data from a repeated-measures research study show that all of the subjects scored about 10 points higher in treatment I than in treatment II. These data will produce ______.
small sample variance and large t statistic
The variability of the scores in a sample tends to be _______ the variability of the scores in the population from which the sample was obtained
smaller than
Standard Deviation=
sqrt(SS/N)
Variance=
standard deviation^2
A population of N = 10 scores has a mean of µ = 80. If 5 points are added to every score in the distribution, what is the value of the new mean
still 80
What is the difference between descriptive and inferential statistics? Descriptive statistics ________, while inferential statistics ________
summarize data; determine the probability that results are due to chance
If the null hypothesis is rejected, the researcher can conclude that the results
support the research hypothesis
For a normal distribution with µ = 60 with σ = 8, what is the probability of selecting a score greater than X = 64?
the proportion of the distribution with z-scores greater than 0.50
A researcher computes the pooled variance for two samples and obtains a value of 120. If one of the samples has n = 5 scores and the second has n = 10 scores, then what is the value of the estimated standard error for the sample mean difference?
the square root of (120/5 + 120/10)
A researcher uses a repeated-measures design to compare individuals' performance before treatment with their performance after treatment. If all of the participants show improved performance of 8 or 9 points after treatment, then the researcher should find ______.
the variance of the difference scores in near 0
The null hypothesis is rejected whenever
there is a low probability that the obtained results could be due to random error.
How would you test the hypothesis that a new stress reduction program really works
try to disprove the hypothesis that it does work
When is a result considered statistically significant?
when the results are so extreme the null hypothesis is rejected
