Analyze This Thing: What Is a Good Item?
DIRECTIONS: RESPOND TO THE FOLLOWING LEARNER DISCUSSION. CITE REFERENCES USING APA FORMAT PLEASE.
According to Cohen, Swedilk, &Sturman (2010), an item-difficulty index is deemed optimal at p=.60 for a five- option multiple choice item and p=.75 for a two option (true or false) item. In the item-discrimination index the higher the value the more it distinguishes between high and low score examinees. If the value is a negative, there is more of a chance of the low scoring examinees to answer the item correctly than a high scoring examinee.
Based on the THING test, Item 2 shows an optimal difficulty between items with a p=.60 on the item difficulty index and some discrimination between examinees d=.20 on the item-discrimination index. The item can still be used but Item 3 would be the most ideal with p=.60, which is the optimal item difficulty on a five-option multiple choice item, and a d=.60 on the item-discrimination index that shows a higher discrimination between high and low scoring examinees.
Item 1 indicates that it is too easy with an item-difficulty index of p=1.00 signifying that everyone that took that test got the answers correctly. The item-discrimination index is a d=0.00 which indicates that there was no discrimination between the examinees that usually score high and those that score low
Item 4, although it shows an optimal difficulty, p=.60, it has an item-discrimination index of d=-.100 indicating that low-scoring examinees are more likely to get that question correctly than their high-scoring peers, therefore, I would also eliminate this item
Reference:
Cohen, R. J., Swerdlik, M. E., &Sturman, E. (2012). Psychological testing and assessment: an introduction to tests and measurement. New York, NY: McGraw-Hill.