Reprinted with permission. One of the unique features of some health psychology tests like the BHI and the P3 is that, unlike most other psychological inventories, they are double-normed. This means that there are two reference or norm groups. At first glance, it may seem somewhat confusing that each scale produces two different scores. However, once this is understood, it can be a powerful tool to extract more accurate information from a test protocol.
Psychometric Considerations Let's begin with a brief reminder about T-scores.
A T-score is a standardized score, based on a normal curve. A T-score of 50 is equal to the average score of some comparison or norm group. Approximately two-thirds of the scores in that norm group will fall between a T score of 40 and a T score of 60. This is the average range. A T of 40 is roughly equivalent to the 16th percentile, and a T is roughly equivalent to the 84th percentile rank.