Rit & Rir

Question 1

What is the Rit value?

Answer 1

The Rit value is a correlation coefficient. It measures the correlation between an individual item’s score (i) and the total score on the test (t).

It measures how well an item discriminates.

The Rit value is between -1 and 1.

Question 2

What would an Rit value of 1 mean?

Answer 2

An Rit value of 1 shows that all students who scored highly on the test got this answer right.

Question 3

What are good and bad Rit values?

Answer 3

0.35 and above: good to very good
0.25-0.35: average to good
0.15-0.25: bad to average
Negative or up to 0.15: very bad to bad

Question 4

What is the Rir value?

Answer 4

The Rir value measures the correlation between an individual item’s score (i) and the rest of the test (r), excluding that individual item.

Question 5

When should you use Rir instead of Rit?

Answer 5

It’s better to use Rir when the test has more than 25 questions.

Question 6

How many candidates do you need for a reliable Rit value?

Answer 6

Ideally over 50 candidates.

Question 7

Case study
The Rit value is negative or exactly 0. What do you recommed?

Answer 7

Check if the answer key is correct.
If so, take the question out.
If not, adjust the answer key and rerun the analysis.

Question 8

Case study
The Rit value is between 0 and 0.15. What do you recommend?

Answer 8

This question does not discriminate. If the p-value is also low, take out the question.