Problem: In an item analysis, the upper group and the lower group both consist of 42 students. In the upper group, 34 got the answer to an item correct; in the lower group, 16 got it correct.
a. What is the index of difficulty for this item?
b. What is the index of discrimination for this item?
c. Based upon your responses to parts (a) and (b), how would you describe the characteristics of the item? For example, is it a good item? Why or why not.