Ill. Admin. Code tit. 23, pt. 25, subpt. L, app A - Statistical Test Equating - Licensure Testing System
The Z-score formula set forth below will be used in all cases except where none of the scorable items on a test form has appeared on any previous test form. In such cases, the linear equating formula will be used.
Z-Score Formula
The following formula is used for z-score equating.
1. Define:
Click here to view image
2. Set zx = zy
Click here to view image
3. In order to find the equivalent passing score on the new form, solve for Xi, where Yi = the passing score on the previous form rounded to one decimal place.
Click here to view image
The linear equating formula is as follows.
1. Define:
Click here to view image
2. Compute estimated descriptive statistics for the total group (i.e., candidates from new and previous test form administrations).
Click here to view image
3. In order to find the equivalent passing score on the new form, solve for Xi, where Yi = the passing score on the previous form rounded to one decimal place.
Click here to view image
Notes
State regulations are updated quarterly; we currently have two versions available. Below is a comparison between our most recent version and the prior quarterly release. More comparison features will be added as we have more versions to compare.