The formula for calculating percentiles is given as: B / T * 100 = percentile
easyCBM tests are largely norm-referenced fundamental skills assessments. Thus, a student’s performance is compared to national norms––scores based on a large nationally-representative
For example, a perfect 20/20 on the Grade 3 Winter Benchmark in Vocabulary is represented by the 87th percentile in reporting because, in the norming sample, 87% of students scored below 20/20 on the Grade 3 Winter Benchmark in Vocabulary. Or, in other words, 13% of students in the norming sample scored 20/20 on that measure.
For most easyCBM test forms we calculate a percentile for every possible score (within reason…i.e., for oral/passage reading fluency, once we get to 99th percentile for a given raw score there is no need to keep calculating percentiles for higher scores) using that basic formula for students included in the norming sample.