Graduate Psychometrics

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University of Phoenix Material

 

Dr. Zak Case Study

Instructions

 

Read the following case study. Use the information in the case study to answer the accompanying follow-up questions. Although questions 1 & 2 have short answers, you should prepare a 150- to 200-word response for each of the remaining questions.

 

Case Study

 

Dr. Zak developed a test to measure depression. He sampled 100 university students to take his five item test. The group of students was comprised of 30 men and 70 women. In this group, four persons were African American, six persons were Hispanic, and one person was Asian. Zak’s Miraculous Test of Depression is printed below:

 

1. I feel depressed: Yes No

 

2. I have been sad for the last two weeks: Yes No

 

3. I have seen changes in my eating and sleeping: Yes No

 

4. I don’t feel that life is going to get better: Yes No

 

5. I feel happy most of the day: Yes No

 

Yes = 1; No = 0

 

The mean on this test is 3.5 with a standard deviation of .5.

 

Follow-Up Questions

 

1. Sally scores 1.5 on this test. How many standard deviations is Sally from the mean? (Show your calculations)

 

 

 

 

 

2. Billy scores 5. What is his standard score?

 

 

 

 

 

3. What scale of measurement is Dr. Zak using? Do you think Dr. Zak’s choice of scaling is appropriate? Why or why not? What are your suggestions?

 

 

 

 

 

 

 

 

4. Do you think Dr. Zak has a good sample on which to norm his test? Why or why not? What are your suggestions?

Dr. Zak does not have a good sample on which to norm his test. Dr. Zak’s sample size that he chose for his assessment does not have enough diversity to be considered reliable, credible, applicable, or valid. Because of the lack of equity in males versus females and diversity within race and ethnicity, Dr. Zak’s does not have a good sample to norm his test. To help Dr. Zak norm his test, he needs to switch up the characteristics of his sample size. First, Dr. Zak needs to ensure he has a fair comparison between males versus females. Right now, he only has 30 females and 70 males, which is not painting a fair picture to qualify as the norm. He should select a sample size less lopsided in terms of gender. Further, within that sample of 100, only eleven people are of a different culture. This is not representative of the “melting pot” society that depicts the state of the United States. Dr. Zak should make a change to include representative sizes of all different cultures to obtain more reliable results from his assessment.

 

 

 

 

 

 

5. What other items do you think need to be included in Dr. Zak’s domain sampling?

 

 

 

 

 

 

 

 

6. Suggest changes to this test to make it better. Justify your reason for each suggestion supporting each reason with psychometric principles from the text book or other materials used in your course.

 

 

 

 

 

 

 

 

7. Dr. Zak also gave his students the Beck Depression Inventory (BDI). The correlation between his test and the BDI was r =.14. Evaluate this correlation. What does this correlation tell you about the relationship between these two instruments?

 

 

 

 

 

 

 

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