PSYCH 248: Statistical Methods in Psychology
Exam 1 Review: Chapters 1-5
Part I: Multiple Choice: Please read each question carefully and pick the best choice!
1. A study tested whether the consumption of alcohol slows reaction time. One group of
randomly selected participants drank a placebo that tasted like, but did not contain alcohol,
while another group drank just enough alcohol, given their body weight, to become legally
drunk. After waiting a sufficient amount of time for the effects of the alcohol to occur, both
groups pressed a button as soon as they could whenever a light turned on. How long it took
the participants to press the button was recorded. All participants had normal vision. What
is the dependent variable in this study?
A. Whether or not the participant drank alcohol
B. How long it took the participant to press the button when the light came on
C. All participants had normal vision
D. None of the above – this study is a correlational study and does not have a dependent
variable.
2. What are two characteristics of rating scales that allow researchers to use these values on
an interval scale of measurement?
A. Values on an interval scale have a true zero but are not equidistant.
B. Values on an interval scale have differences and a true zero.
C. Values on an interval scale are equidistant and have a true zero.
D. Values on an interval scale are assumed to be equidistant but do not have a true zero.
3. Which of the following is a discrete variable?
A. The amount of time remaining on this exam
B. the number of questions on this exam
C. the width of the paper that this exam is printed on
D. All of the above
4. A coffee shop wants to know the temperature of coffee that most people prefer. They
brew coffee at the typical temperature for the shop and then ask customers “Do you prefer
coffee to be at this temperature?” and record a yes or no answer for each customer. What is
the level of measurement of the way they measured preferred temperature?
A. Nominal
B. Ordinal
C. Interval
D. Ratio
5. A standardized test of achievement yields scores between 300 and 700. If you were to
create a grouped frequency distribution of the scores, what would be the most appropriate
width for the class interval?
A. 10
B. 20
C. 50
D. 100
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6. The distribution to the right is
A. Symmetrical.
B. Normal.
C. Negatively skewed.
D. Positively skewed.
7. The mean score on an exam is 73 points. The instructor adds 10 points to everyone’s
score. What is the mean score on the exam after the 10 points have been added?
A. 73
B. 83
C. None of the above but I could calculate it given the information in the problem.
D. How should I know? You would have to tell us the exam scores, add ten points to each
one, and then calculate the new mean.
8. An instructor records how long it takes students to finish a statistics test. If the times are
normally distributed, which of the measures of central tendency would be most appropriate
to use with this data?
A. Mode
B. Median
C. Mean
D. Interquartile range
9. A researcher measures how long it takes students to press a button when a loud sound
occurs. He calculates the mode, median and mean of the data and finds that the mode is less
than the median, which is less than the mean. Which of the following is most likely true
about the distribution of scores?
A. They are normally distributed.
B. They are symmetrically distributed, but not necessarily normally distributed.
C. They are negatively skewed.
D. They are positively skewed.
10. The variance of a population
A. Equals the mean of the squared deviation scores.
B. equals SS/df.
C. is represented by σ2
D. All of the above are true.
11. A sample group of participants is weighed in anticipation of a study. Their weights are
found to be normally distributed, with a mean of 163.4 lbs. and a standard deviation of
15.8lbs. What is the probability that a participant, selected at random, will measure exactly
of 163.4 lbs?
A. p=1
B. p=0.5
C. p=0
D. All of the above
12. What is the standard deviation for the following set of scores: 6, 3, 5, 6, 2, 2?
A. 1.73
C. 1.3
B. 3
D. 18
13. A population has sum of squared deviations, SS=200 and variance, σ2 =5. How many
scores are in the population?
A. 10
C. 30
B. 20
D. 40
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Part II: True & False
14. An expected value is the average expected outcome for a given random
variable.
15. A probability distribution is the distribution of probabilities for each outcome of a
random variable.
16. Frequency polygons are plotted at the endpoint of each interval, whereas ogives are
plotted at the lower boundary of each interval.
17. The mean is most appropriate in describing data that are normally distributed on an
interval or ratio scale of measurement.
18. The standard deviation measures the average distance that scores deviate from their
mean.
19. Descriptive statistics are used to help the researcher infer the unknown parameters in a
given population.
20. Inferential statistics are procedures used to summarize, organize, and make sense of a
set of scores called data.
21. An experiment is the only method that can demonstrate cause-and-effect relationships
between variables.
Part III: Short Response
22. A researcher selects a sample from a population of 432 people, 212 of whom are
women. What is the probability of selecting a woman as the first participant in this study?
23. The probability that someone in the human population has an AB blood type is
approximately p = .08; the probability that someone in the human population has an O
blood type is approximately p = .25. Knowing that each individual can have one and only
one blood type, what is the probability that a person has
(a) an AB and an O blood type and
(b) an AB or an O blood type?
24. Two outcomes are mutually exclusive when ___________________________
25. A hypothetical population consists of eight individuals ages 13, 14, 17, 20, 21, 22, 24,
and 30 years.
a. What is the probability that a person in this population is a teenager?
b. What is the probability of selecting a participant older than 30?
c. What is the probability of selecting a participant who is at least 20 years old?
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26. State whether each of the following describes a study measuring a qualitative or
quantitative variable.
a. A researcher distributes open-ended questions to participants asking how they feel
when they are in love.
b. A researcher records the blood pressure of participants during a task meant to
induce stress.
c. A psychologist interested in drug addiction injects rats with an attention-inducing
drug and then measures the rate of lever pressing
d. A witness to a crime gives a description of the suspect to the police.
27. Explain why the median is preferred to the mean as a measure of central tendency for a
skewed distribution.
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28. On the following graph below, please label the independent variable (x) and dependent
variable (y):
29. State whether each of the following describes an experiment, a quasi-experiment, or a
correlational method.
a. A researcher tests whether the dosage level of some drug (low, high) causes significant
differences in health.
b. A researcher tests whether citizens of differing political affiliations (Republican,
Democrat) will show differences in attitudes toward morality.
c. A researcher measures the relationship between annual income and life satisfaction.
30. What is the difference between an experimental and correlational research?
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