Quick data guide

YARC provides three different types of normative scores:

• standard scores
• percentile ranks
• age-equivalent scores

We would urge teachers using YARC to rely on standard scores rather than age-equivalent scores or percentile ranks for interpreting and expressing the scores obtained on the test.

For most purposes, standard scores are the best way of expressing a pupil’s performance on tests of ability. They express a child’s score in relation to the spread of scores obtained by a sample of children of the same age. Here’s a guide to interpreting standard scores:

A percentile rank gives the pupil’s ranking in relation to other pupils of the same age. A percentile rank of 50 means the pupil has performed as well as or better than 50% of children of the same age i.e., a percentile rank of 50 is the average score for the child’s age.

However, percentiles only express a child’s relative standing and, owing to their mathematical properties, these scores cannot be meaningfully combined or averaged.

Also known as ‘reading ages’, age-equivalent scores are ages at which a given ‘ability score’ is the average. For each component of YARC Early Reading, a pupil’s test raw score is converted to an ability score. The ability score expresses a pupil’s ability on an arbitrary scale of measurement. These ability scores can then be expressed in terms of the average age at which such a score was obtained in the standardisation sample.

However, age-equivalent scores do not contain any information about the spread of scores on a test at a particular age. Given that pupils whose scores need to be compared will often differ in age, age-equivalent scores become very cumbersome to interpret.