An introduction to standardised scores

Many people will remember test scores from their school days such as ‘7 out of 10’ for a primary school spelling test, or ‘63%’ for one of their secondary school exams. Such scores, known as raw scores, are readily understandable and useful in indicating what proportion of the total marks a person has gained in a test. However, these scores are less useful in enabling teachers to compare pupils’ performance meaningfully between one test and another, and to monitor progress over a period of time. This is because raw scores do not account for factors such as the difficultly of a test or performance relative to other test takers.

Many professionally produced tests, including NFER Tests for years 1-5 give additional outcomes, beyond simple proportions or percentages. One of these measures is standardised scores.


Why use standardised scores?

Standardised scores are more useful measures than raw scores (the number or percentage of questions answered correctly) as they enable test-takers to be compared with a large, nationally representative sample that has taken the test prior to publication. Usually, tests are standardised so that the average, nationally standardised score automatically comes out as 100, irrespective of the difficulty of the test. This means teachers can readily identify whether a test-taker is above or below the national average.

As standardised scores are converted onto a common scale they enable meaningful comparisons between scores from other standardised tests. Standardised scores from most educational tests cover the same range, from 70 to 140. Hence a pupil's standing in, say, mathematics and English can be compared directly using standardised scores. A pupil’s standardised score can also be tracked from test to test to monitor whether progress is being made.

Standardised scores may also make an allowance for the different ages of test takers. This is known as an age-standardised score. In a typical class in England and Wales, the oldest pupils can be up to 12 months older than the youngest. Almost invariably, in ability tests taken in the primary and early secondary years, older pupils achieve slightly higher raw scores than younger pupils on average. However, age-standardised scores are derived in such a way that the ages of the pupils are taken into account by comparing a pupil with others of the same age (in years and months) in the nationally representative sample. Thus a younger pupil may gain a lower raw score than an older pupil, but have a higher standardised score. This is because the younger pupil is being compared with other younger pupils in the reference group and has a higher performance relative to his or her own age group. Age-standardised scores are therefore beneficial in allowing meaningful comparisons between pupils within a school. However, please be aware that not all standardised tests are age-standardised and ask your test provider if you are unsure.


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For further short reads on classroom assessment, visit our Introduction to Assessment page.

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