PSYCH 655- Psychometrics Assignment- University of Phoenix
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 responsefor 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?
Reliability and Validity Worksheet
Instrument Reliability
A reliable instrument is one that is consistent in what it measures. If, for example, an individual scores highly on the first administration of a test and if the test is reliable, he or she shouldscore highly on a second administration.
Imagine that you are conducting a study for which you must develop a test in mathematics for 7th-grade students. You develop a 30-point test and distribute it to a class of 12,7th-grade students. You then administer the test again one month later to the day. The scores of the students on the two administrations of the test are listed below. UseMicrosoft® Excel® or IBM®SPSS® to create a scatterplot with the provided scores, formatted as shown in the example graph. What observations can you make about the reliability of this test? Explain.
30-POINT TEST 30-POINT TEST
(FIRST ADMINISTRATION) (SECOND ADMINISTRATION)
A 17 15_______________
B 22 18_______________
C 25 21_______________
D 12 15_______________
E 7 14_______________
F 28 27_______________
G 27 24_______________
H 8 5_______________
I 21 25_______________
J 24 21_______________
K 27 27_______________
L 21 19_______________
What Kind of Validity Evidence: Content-Related, Criterion-Related or Construct-Related?
A valid instrument is one that measures what it says it measures. Validity depends on the amount and type of evidence there is to support one's interpretations concerning data that has been collected. This week, you discussed three kinds of evidence that can be collected regarding validity: content-related, criterion-related, and construct-related evidence.
Each question below represents one of these three evidence types. In the space provided, write content if the question refers to content-related evidence, criterion if the question related to criterion-related evidence, and construct if the question refers to construct-related evidence of validity.
1. How strong is the relationship between the students' scores obtained using this instrument and their teacher's rating of their ability?
2. How adequately do the questions in the instrument represent that which is being measured?
3. Do the items that the instrument contains logically reflect thatwhich is being measured?
4. Are there a variety of different types of evidence (test scores, teacher ratings, correlations, etc.) that all measure this variable?
5. How well do the scores obtained using this instrument predict future performance?
6. Is the format of the instrument appropriate?
Answer each question using 175 words or more.
1. What are reliability and validity?
2. Is there a difference when we talk about reliability and validity about tests and assessments vs. research or is it the same?
3. What is a psychological construct? Why is it important? Why are we talking about it in this course of Psychometrics?
Format your assignment according to the following formatting requirements:
1. The answer should be typed, double spaced, using Times New Roman font (size 12), with one-inch margins on all sides.
2. The response also includes a cover page containing the title of the assignment, the student's name, the course title, and the date. The cover page is not included in the required page length.
3. Also include a reference page. The Citations and references should follow APA format. The reference page is not included in the required page length.