Conditional Standard Error of Measurement

The conditional standard error of measurement (CSEM) describes how much measurement error a test score carries at each point along the score scale, rather than as a single average. A test typically measures more precisely in some score ranges than others — often best near the middle and worst at the extremes — and the CSEM captures that variation. Recognized in test theory by Lord and required by the Standards for Educational and Psychological Testing, it is essential for honest score reporting, especially near cut scores where classification decisions are made.