Time to Practice: Week 2
Complete Parts A, B, and C below.
Part A
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 74.13 and the standard deviation is 9.98.
|
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 and the standard deviation = 6.38. Draw a small picture to help you see what is required.
a. What is the probability of a score falling between a raw score of 70 and 80?
b. What is the probability of a score falling above a raw score of 80?
c. What is the probability of a score falling between a raw score of 81 and 83?
d. 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?
From Salkind (2011). Copyright © 2012 SAGE. All Rights Reserved. Adapted with permission.
Part B
The 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 Textbook Resources link.
The data sets for problems 5 and 6 can be found through the Pearson Materials in the Textbook Resources link. The data is listed in the data file named Lesson 20 Exercise File 1. Answer Exercises 5 and 6 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).
5. 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
6. Using IBM® SPSS® software, create a frequency table to summarize the data on the educational level variable. Copy and paste the output from IBM® SPSS® into this worksheet.
From Green & Salkind (2011). Copyright © 2012 Pearson Education. All Rights Reserved. Adapted with permission.
Part C
Answer the questions below in at least 90 words. Be specific and provide examples when relevant.
Cite any sources consistent with APA guidelines.
Question
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?
What are the four different levels of measurement? Explain and provide examples.
How does understanding probability help you understand statistics?