Topics: Standard deviation, Arithmetic mean, Statistics Pages: 2 (351 words) Published: January 18, 2011
University of Phoenix Material
Dr. Zak Case Study
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 to 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:

I feel depressed:Yes No

I have been sad for the last two weeks:YesNo

I have seen changes in my eating and sleeping:YesNo

I don’t feel that life is going to get better:YesNo

I feel happy most of the day:YesNo

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?

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. For each suggestion justify your reason 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 us about the...
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