1. Classroom Assessment
Ways to improve tests

2. Improving Tests: Judgmental Procedures
Check your tests and items: Do they…
adhere to item-writing guidelines?
lead to score-based inferences?
accurately reflect the content?
provide representative coverage of all content and learning targets?
provide fair and unbiased assessment?

3. Improving Tests: Empirically Based Procedures
Difficulty index (p):
Number Getting Item Correct
p = —————————————
Total Number of Examinees R
= —— T

4. Improving Tests: Empirically Based Procedures
Item-Discrimination Index (D).
D = Correlation between an item and the total test score.
Indicates the extent to which an item tends to be answered correctly by those who score high on the test.
Can be positively discriminating or negatively discriminating, or non-discriminating.

5. Empirically Based Procedures: Discrimination Index
Type of Item Proportion Correct
Positive Discriminator High > Low
Negative Discriminator High < Low
Non-discriminator High = Low
Popham gives instructions for for calculating and interpreting D on pages

6. Empirically Based Procedures: Distracter Analysis
Particularly useful when an item needs revision.
Item No. xx Alternatives
(p = .4, D = -.5) A B C D* O
Upper 15 students
Lower 15 students
Why did nearly half the upper 15 students select alternative B?

7. Empirically Based Procedure for Criterion-referenced Tests
Two general approaches:
Use a pretest and a posttest.
D = p(Post) - p(Pre)
Use two groups of students.
One having received instruction.
One having not received instruction.
D = p(Instructed) - p(Not-Instructed)

8. End