PSYC 215 Introductory Stats for Behavioral & Social Sciences

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PSYC 215
Introductory Stats for Behavioral & Social Sciences
PRACTICE EXAM #1
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Problem 1: Violent Crime
The following data table organizes the rate of violent crimes per 1,000 people in several California counties. These data
were reported to the State of California in 2018.

On your own, calculate the sample mean, median, mode, range, sum of squares, sample variance, and sample
standard deviation for the county violent crimes data.
1. What is the correct calculation for the sample mean?
a.
37.12
9
b. 38.55
9
c.
36.23
9
d. 39.66
9
2. What is the correct calculation for the sample standard deviation?
a. √1.31
b. √1.48
c. √1.72
d. √1.68
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Springfield County is a fictional county with a similar population size as the counties listed on page 2. The Springfield
County Supervisor wants to know if Springfield County had a higher crime rate than the comparison counties. In 2018,
Springfield County reported 5.71 violent crimes per 1,000 people. A statistics consultant performed the analysis using an
alpha level of 0.05 and used the California county data from page 2 to answer the County Supervisor’s question.
On your own, determine the independent variable, dependent variable, H0 and Ha.
3. What kind of test should the statistics consultant perform?
a. Two-tailed
b. Not enough information is provided in the problem to determine the answer.
c. One-tailed (low)
d. One-tailed (high)
4. What is the z-score for Springfield County? Use the formula to the right.
a. +0.53
b. +1.38
c. -0.69
d. -1.86
On your own, mark zcrit, shade the region of rejection, and place a flag for zobt. You may use the z-distribution
below.
5. Based on the result of the z-test, what is the proper conclusion?
a. Fail to reject the null hypothesis. The result is statistically significant. There is evidence that Springfield
County has a higher crime rate than the comparison counties.
b. Reject the null hypothesis. The result is nonsignificant. There is no evidence that Springfield County has a
higher crime rate than the comparison counties.
c. Reject the null hypothesis. The result is statistically significant. There is evidence that Springfield County
has a higher crime rate than the comparison counties.
d. Fail to reject the null hypothesis. The result is nonsignificant. There is no evidence that Springfield County
has a higher crime rate than the comparison counties.
SX
XX
z
–
=
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Problem 2: County Spending
The following table shows the county-level expenditures on Libraries, Education, Recreation, and Culture for 2017-2018.
The total dollar amounts were divided by the number of residents in each county to yield the average amount spent per
resident.

On your own, calculate the sample mean, median, mode, range, sum of squares, sample variance, and sample
standard deviation for the county spending data.
6. What is the median for the sample data?
a. $24.81
b. $24.79
c. $24.10
d. $24.66
7. What is the correct calculation for the sample variance?
a.
330.88
9
b. 1064.18
9
c.
977.42
9
d. 1061.54
9
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Back in Springfield County, the County Supervisor wants to know whether their local government’s spending is any different
from the California counties. During 2017-2018, the Springfield Board of Supervisors approved spending an average of
$50.60 per resident on libraries, education, recreation, and culture. To answer the politician’s question, a statistics
consultant used the county data from page 5 and performed the analysis using an alpha level of 0.01.
On your own, determine the independent variable, dependent variable, H0 and Ha.
8. What kind of test should the statistics consultant perform?
a. Two-tailed
b. One-tailed (high)
c. One-tailed (low)
d. Not enough information is provided in the problem to determine the answer.
9. What is the z-score for Springfield County? Use the formula to the right.
a. +4.71
b. -0.08
c. -0.18
d. -0.95
On your own, mark zcrit, shade the region of rejection, and place a flag for zobt. You may use the z-distribution
below.
10. Based on the result of the z-test, what is the proper conclusion?
a. Reject the null hypothesis. The result is nonsignificant. There is no evidence that Springfield County’s
spending is different from the California counties.
b. Reject the null hypothesis. The result is statistically significant. There is evidence that Springfield County’s
spending is different from the California counties.
c. Fail to reject the null hypothesis. The result is statistically significant. There is evidence that Springfield
County’s spending is different from the California counties.
d. Fail to reject the null hypothesis. The result is nonsignificant. There is no evidence that Springfield County’s
spending is different from the California counties.
SX
XX
z
–
=
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Problem 3: “Walkability” Scores
The following data table summarizes the current “walkability” scores for several California cities and neighborhoods
according to www.walkscore.com. Cities with higher scores tend to have businesses, stores, and restaurants concentrated
in one area and are generally considered friendly to pedestrians. Cities with lower scores tend to be communities where a
car or public transportation is necessary to navigate the area.

On your own, calculate the sample mean, median, mode, range, sum of squares, sample variance, and sample
standard deviation for the city/neighborhood walkscores.
11. What is the range for the sample data?
a. 39 – 95
b. 39 – 97
c. 66 – 98
d. 77 – 98
12. What is the correct calculation for the sample mean?
a.
803
9
b. 512
9
c.
776
9
d. 523
9
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The Springfield County city planners were curious whether Downtown Springfield was less “walkable” than the California
cities. The County Supervisor sent the data analysis request to the statistics consultant who used an alpha level of 0.01.
The same data from page 8 were also forwarded to the consultant for analysis. Currently, Downtown Springfield is rated 68
on walkscore.com.
On your own, determine the independent variable, dependent variable, H0 and Ha.
13. What kind of test should the statistics consultant perform?
a. One-tailed (high)
b. One-tailed (low)
c. Two-tailed
d. Not enough information is provided in the problem to determine the answer.
14. What is the z-score for Downtown Springfield? Use the formula to the right.
a. -1.80
b. +2.42
c. -3.19
d. +1.79
On your own, mark zcrit, shade the region of rejection, and place a flag for zobt. You may use the z-distribution
below.
15. Based on the result of the z-test, what is the proper conclusion?
a. Fail to reject the null hypothesis. The result is statistically significant. There is evidence that Downtown
Springfield is less “walkable” than the California cities.
b. Reject the null hypothesis. The result is nonsignificant. There is no evidence that Downtown Springfield is
less “walkable” than the California cities.
c. Reject the null hypothesis. The result is statistically significant. There is evidence that Downtown
Springfield is less “walkable” than the California cities.
d. Fail to reject the null hypothesis. The result is nonsignificant. There is no evidence that Downtown
Springfield is less “walkable” than the California cities.
SX
XX
z
–
=
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Answer Sheet

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