1. Descriptive Statistics
N
Minimum
Maximum
Mean
Std. Deviation
total
105
50
125
100.07
14.483
Zscore(total)
105
-3.45694
1.72157
.0000000
1.00000000
Valid N (listwise)
105
Question 1
What is the sample mean (M) and sample standard deviation (s)
for total? You will use these values in Question 2 below.
[Answer here in complete sentences. Also insert the output
from SPSS here. Replace this prompt and the prompts below,
using as much space as necessary to answer questions.]
Question 2

2. A z score for this sample is calculated as [(X – M) ÷ s]. Locate
Case #53’s unstandardized total score (X) in the Data Editor. In
the formula below, replace X, M, s, and ? to show how the z
score in Ztotal is derived for Case #53.
(X – M ) ÷ s = ?
Question 3
Run Descriptives… on Ztotal. What are the mean and standard
deviation of Ztotal? (Hint: “0E7” in SPSS is scientific notation
for 0). Are the mean and standard deviation what you would
expect? Justify your answer.
[Answer here in complete sentences. Also place the SPSS output
here.]
Question 4
Case number 6 has a Ztotal score of 1.51. What does a z value
of 1.51 represent?
[Answer here in complete sentences.]
Question 5
Identify the case with the lowest z score. Refer to Appendix A
in the Warner (2013) text. Interpret the percentile rank of this z
score rounded to whole numbers.
[Answer here in complete sentences.]
Question 6
Identify the case with the highest z score. Refer to Appendix A
in the Warner (2013) text. Interpret the percentile rank of this z
score rounded to whole numbers.
[Answer here in complete sentences.]
Section 2: Cases Studies of Type I and Type II Errors
Question 7
A jury must determine the guilt of a criminal defendant (not
guilty, guilty). Identify how the jury would make a correct
decision. Analyze how the jury would commit a Type I error
versus a Type II error.
[Answer here in complete sentences.]
Question 8
An I/O psychologist asks employees to complete surveys
measuring job satisfaction and organizational citizenship

3. behavior. She intends to measure the strength of association
between these two variables. The researcher is concerned that
she will commit a Type I error. What research decision
influences the magnitude of risk of a Type I error in her study?
[Answer here in complete sentences]
Question 9
A clinical psychologist is studying the efficacy of a new drug
medication for depression. The study includes a placebo group
(no medication) versus a treatment group (new medication). He
then measures the differences in depressive symptoms across
the two groups.
What would a Type I error represent within the context of his
study? How can he reduce the risk of committing a Type I
error? How does this decision affect the risk of committing a
Type II error?
[Answer here in complete sentences.]
Section 3: Case Studies of Null Hypothesis Testing
Question 10
You are running a series of statistical tests in SPSS using the
standard criterion for rejecting a null hypothesis. You obtain the
following p values.
Test 1 calculates group differences with a p value = .07.
Test 2 calculates the strength of association between two
variables with a p value = .50.
Test 3 calculates group differences with a p value = .001.
For each test below, state whether or not you reject the null
hypothesis. For each test, also explain what your decision
implies in terms of group differences (Test 1 and Test 3) and in
terms of the strength of association between two variables (Test
2).
Test 1 (group differences) =
Test 2 (strength of association) =
Test 3 (group differences) =
Question 11
A researcher calculates a statistical test and obtains a p value of
.86. He decides to reject the null hypothesis. Is this decision

4. correct, or has he committed a Type I or Type II error? Explain
your answer.
[Answer here in complete sentences]
Question 12
You are proposing a research study that you would like to
conduct while attending Capella University. During the
proposal, a committee member asks you to explain in your own
words what you meant by saying “p less than .05.” Provide an
explanation.
[Answer here in complete sentences]
References
Provide references if necessary. This concludes Unit 4
Assignment 1. Save your answers and upload this template to
the assignment area.