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Time to Practice – Week Two
PSYCH/625 Version 1
University of Phoenix Material
Time to Practice – Week Two
Complete Parts A, B, and C below.
Part A
Some questions in Part A require that you access data from Statistics for People Who (Think They) Hate
Statistics. This data is available on the student website under the Student Text Resources link.
1. Why is a z score a standard score? Why can standard scores be used to compare scores from
different distributions?
2. For the following set of scores, fill in the cells. The mean is 70 and the standard deviation is 8.
Raw score
Z score
68.0
?
?
–1.6
82.0
?
?
1.8
69.0
?
?
–0.5
85.0
?
?
1.7
72.0
?
3. Questions 3a through 3d are based on a distribution of scores with
= 6.38. Draw a small picture to help you see what is required.
a.
b.
c.
d.
and the standard deviation
What is the probability of a score falling between a raw score of 70 and 80?
What is the probability of a score falling above a raw score of 80?
What is the probability of a score falling between a raw score of 81 and 83?
What is the probability of a score falling below a raw score of 63?
4. Jake needs to score in the top 10% in order to earn a physical fitness certificate. The class mean is
78 and the standard deviation is 5.5. What raw score does he need?
5. Who is the better student, relative to his or her classmates? Use the following table for information.
Math
Class mean
81
Class standard
deviation
2
Copyright © 2013 by University of Phoenix. All rights reserved.
1
Time to Practice – Week Two
PSYCH/625 Version 1
Reading
Class mean
87
Class standard
deviation
10
Raw scores
Math score
Reading score
Average
Noah
85
88
86.5
Talya
87
81
84
Math score
Reading score
Average
Z-scores
Noah
Talya
From Salkind (2011). Copyright © 2012 SAGE. All Rights Reserved. Adapted with permission.
Part B
Some questions in Part B require that you access data from Using SPSS for Windows and Macintosh.
This data is available on the student website under the Student Text Resources link.
The data for Exercises 6 and 7 are in the data file named Lesson 20 Exercise File 1. Answer Exercises 6
and 7 based on the following research problem:
Ann wants to describe the demographic characteristics of a sample of 25 individuals who completed a
large-scale survey. She has demographic data on the participants’ gender (two categories), educational
level (four categories), marital status (three categories), and community population size (eight categories).
6. Using IBM® SPSS® software, conduct a frequency analysis on the gender and marital status
variables. From the output, identify the following:
a. Percent of men
b. Mode for marital status
c. Frequency of divorced people in the sample
7. Using IBM® SPSS® software, create a frequency table to summarize the data on the educational level
variable.
The data for Exercise 8 is available in the data file named Lesson 21 Exercise File 1.
8. David collects anxiety scores from 15 college students who visit the university health center during
finals week. Compute descriptive statistics on the anxiety scores. From the output, identify the
following:
a.
b.
c.
d.
Skewness
Mean
Standard deviation
Kurtosis
Copyright © 2013 by University of Phoenix. All rights reserved.
2
Time to Practice – Week Two
PSYCH/625 Version 1
From Green & Salkind (2011). Copyright © 2012 Pearson Education. All Rights Reserved. Adapted with
permission.
Part C
Complete the questions below. Be specific and provide examples when relevant.
Cite any sources consistent with APA guidelines.
Question
Answer
What is the relationship between reliability and
validity? How can a test be reliable but not
valid? Can a test be valid but not reliable? Why
or why not?
How does understanding probability help you
understand statistics?
How could you use standard scores and the
standard distribution to compare the reading
scores of two students receiving special reading
resource help and one student in a standard
classroom who does not get special help?
In a standard normal distribution: What does a z
score of 1 represent? What percent of cases fall
between the mean and one standard deviation
above the mean? What percent fall between the
mean and –1 to +1 standard deviations from
the mean? What percent of scores will fall
between –3 and +3 standard deviations under
the normal curve?
Copyright © 2013 by University of Phoenix. All rights reserved.
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