The Percentile Program

The Percentile Program handles all aspects of percentile calculations within the context of neuropsychological and psychological assessment. The Percentile Program will:


The Percentile Program is highly accurate. The algorithm to calculate percentiles uses a polynomial approximation of the cumulative area under the normal curve. This algorithm is described in the "Handbook of Mathematical Functions with Formulas, Graphs & Mathematical Tables", edited by Milton Abramowitz and Irene A. Stegun (published by Dover Publications, 1972). The absolute error in this algorithm is less than 7.5 x 10-8, making these calculations accurate to about seven decimal places.

Inverse percentile calculations are accomplished with an approximation of the inverse normal cumulative distribution function. The absolute error in this algorithm is less than 1.15 x 10-9, making inverse percentile calculations accurate to about eight decimal places.


Raw Scores Module

Score Converter Module

Age Calculator

Numerical Calculator


Click below to download the Percentile Program installation package (2.4 MB):

Click to download and install the Percentile Program