A few years ago, students in my class created a Psychology Achievement Test (PAT). Data from a shortened version of this test (30 items) will be used for this exercise. We have data from 40 students who took the test. Your job will be to conduct an item analysis and decide which items to drop from the test. The raw data are contained in an Excel file. The file also contains information about the students who took the exam. Specifically, we coded whether each participant was a psychology major or not, their sex, and the number of psychology courses they had taken in college.
For this assignment, please complete the following steps:
1. Calculate and report the item difficulties (p).
2. Calculate and report the item-total correlations.
3. Identify the items that should be removed from the test (there are 8 items that should be removed). For each item that you remove, please provide your reason for removing it.
4. With the items you decide to keep, calculate a new total score (you will have to delete the items from the spreadsheet that you identified in Step 3 and sum across the remaining items).
a. Correlate the new total with each of the following: major, sex, and # of psychology courses (thus, you will compute three correlations).
b. Interpret these correlations. What do they suggest about the validity of the test?