Normal Curve Equivalent. An achievement test norm-referenced sore that describes the performance of a student relative to other students (the norming population). This score is derived from percentile ranks, but in contrast to percentiles (an ordinal scale), NCE provides an equal-interval scale. Students with a zero NCE have maintained their pretest achievement status at posttest. A mean NCE gain significantly different from zero revels that a significant change in achievement status in the student population has occurred from pretest to posttest.