This is an indicator of the amount of dispersion in a score distribution. To calculate variance, the difference of each score from the mean is squared. Then all the squares are added together and divided by the number of scores.

# FAQ Group: Glossary of Terms

## Variability

The dispersion of values from the average. Standard deviation and variance are measures or variability.

## Value Added

This refers to the contribution a school makes to the education of its pupils. If one or more pupils scores higher in National Tests, GCSE or A Level than would have been predicted on the basis of their known earlier level of achievement, the difference is attributed to ‘value-added’ by the school. The concept is usually linked with baseline assessment, since the latter is required to establish the entry level from which the subsequent performance may be judged. Another link is with the term ‘Effective School’, used to designate well-run school which are measurably improving the prospects of their pupils, by adding value.

## Validity

A valid assessment measures what it claims to measure. Evidence may be presented in various ways – satisfactory correlations with other assessments of the same abilities or skills; or with teaches’ estimates of their pupils’s abilities; or with pupils’ subsequent achievements such as their results in a public examinations.

## Test Battery – see Battery

## Teacher Assessment

This can take many forms – such a summative or formative assessment, which may include publishing tests. In the context of the National Curriculum, and the 5-14 Guidelines in Scotland, it is usually used to mean any form of assessment carried out by the teacher, other than the National Tests prescribed by the Government.

## Summative Assessment

This is used for the recording of the overall achievement of a pupil in a systemic way. It occurs at the end of a scheme of work or phase of education, and a norm-referenced assessment is often used for this final summing up of performance.

## Stanine

A stanine (which is abbreviated from ‘standard nine’) is a standard score scale ranging from 1 to 9. Stanines are simple to use and place small difference of score in perspective. Stanines have a mean of 5 and a standard deviation of 2.

## Standardised Test

A standardised test will have been administered to a representative sample of a defined population in order to calculate norms. Norms give information about the performance of this sample. By using the norms as a reference points, teachers can compare the performance of their pupils with the standardised sample. A test can also have standardised administration procedures, whereby strict instructions have to be followed by the administrator.

## Standard Error of Measurement (SEM)

The estimate of the ‘error’ associated with pupils’ obtained score when compared with their hypothetical ‘true’ score. The SEM, which varies from test to test, should be given in the test manual. The band of scores in which we can be fairly certain the ‘true’ score lies, can be calculated from these figures. For example, we can be 95 per cent certain that a pupils’ true score lies in the range ‘obtained score plus or minus 2 SEM’ and 99 per cent certain that it lies in the range ‘obtained score plus or minus 3 SEM’.