T Scores

Synonyms

Demographically-adjusted T score; Normative T score

Definition

T scores are commonly used for neuropsychological normative data. A T score is a special type of standard score. T scores result from a transformation of raw scores to standard scores. The formula for a standard score (i.e., a z score) is provided below.

$$ z = {{x - M} \over {{\rm{SD}}}} $$

where:

• x is a raw score to be standardized.

• M is the mean of the normative sample.

• SD is the standard deviation of the normative sample.

T scores have a mean of 50 and a standard deviation of 10. Standard z scores can be converted to T scores using the formula below.

$$ T = {\rm{1}}0\, {^\ast}\, z + {\rm{50}} $$

(e.g., z = −1, T = 40; z = 1, T = 60)

Current Knowledge

For ease of communication in clinical reports, T scores can be converted to percentile ranks. The percentile rank represents the percentage of scores in a frequency distribution that are lower than the obtained score (e.g., the 50th percentile means that 50% of...