Correct Per Minute Scores and How They Are Adjusted (Equated)
Star CBM assessment scores are shown as Correct Per Minute (CPM). Some CPM scores are adjusted as described below.
Star CBM includes several measures, and each measure has multiple forms. To make the results from all forms in a measure comparable, and to provide a basis for calculating the norm-referenced scores, Star CBM converts (or equates) all Star CBM scores to a common form within each measure. Equating eliminates differences in form difficulty so that scores can be interpreted on the same scale. Star CBM does this in steps:
- Star CBM records the number of correct responses on a form (Correct Count).
- The Correct Count score on all of the other forms is equated to the form that has been identified as the easiest form.
- Star CBM converts the equated correct count to a Correct per Minute (CPM) score. To do this, the equated correct count is multiplied by 60 and divided by the total time the student took on the assessment.
As a result, CPM scores indicate the same level of performance and can be interpreted regardless of the specific form taken in a measure.
Note: Scores for Rapid Color Naming and Rapid Picture Naming are not adjusted. For Passage Oral Reading, scores on Grade 4, Grade 5, and Grade 6 passages are not adjusted.
For detailed information, refer to the Star CBM Reading Technical Manual and the Star CBM Math Technical Manual.