Converting standardised scores to Percentiles
Posted by Cynthia W on 30 December 2006 11:07 PM

The following table shows corresponding percentile scores for a range of Z scores.

Converting to percentile scores

PsyAsia's Psychometric Training Course attendees will recall that to calculate a Z score from a raw score one uses the following formula:

Z score = Raw Score minus Mean divided by Standard Deviation

To convert from any other standard score scale into a Z score, one simply subtracts the mean of the other standard scale from the standard scale score and divides by the standard deviation of the standard score scale.

So, to convert a T score into a Z score:

Z score = T Score minus mean of T score scale (50) divided by standard deviation of a T score scale (10).

See also: What is a percentile score