What is the relationship between the T-scores and the age equivalents?
T-scores and age equivalents offer different information about the child’s performance. The T-score/percentile rank of a child indicates how well he or she has performed relative to other children of the same age. It does not indicate anything about the rate at which the ability in question develops across age. The age equivalent indicates the age at which a child’s performance would be judged as ‘average’ – that is, the age at which 50% of children achieve at least that level of performance. It gives an indication of the extent to which the ability develops across age. However, it gives no indication of the spread of scores achieved by children of the same age as the child being assessed. Since different abilities develop at different rates over age, there will not be a one-to-one relationship between percentiles and age equivalents across different scales. Hence, it is entirely possible that when a child has the same T-score on two different scales, they will not always have the same
