Individual Scale for General Scholastic Aptitude (ISGSA)

M. Robinson & J.S. Boshoff

Certain Education departments in the previous dispensation requested the HSRC to revise and re-standardize the old South African Individual Scale, known as the OSAIS, as they regarded the scale as very useful. After it had been empirically established that the OSAIS was in fact a valid and reliable instrument for measuring intelligence, it was decided to comply with the request and the scale was revised and re-standardised. The ISGSA is consequently the revised version of the OSAIS. The aim with the standardization was to retain as many of the old items as possible in a revised form, to replace certain items, and to include more non-verbal items in such a way that the scale could be administered in a relatively short time.

The ISGSA was standardised for children from 5 to 16 years, with English or Afrikaans as mother tongue. The target group for whom the scale had to measure well is six to twelve-year-olds, in other words primary school children. As the ISGSA is a revised version of the old scale, it is still based on the Binet rationale of the old scale. The format of the old scale was partially retained. It consists of heterogeneous items that are arranged from easy to difficult. The scale was reduced to 80 items, which are divided into blocks of four items each. For each age group testing should commence at a specific block. A base (two blocks in which the testee answers all the items correctly) and ceiling (two blocks in which all the items are failed) are determined for the testee. All the items between the base and the ceiling are administered. The scale measures global cognitive ability and not differentiated abilities, but qualitative analysis by the test user can shed light on the testee’s strengths and weaknesses. The verbal content of the scale is greater than the non-verbal content. For this reason the term scholastic aptitude is used in the scale instead of intelligence. The validity and reliability data in the manual indicate that the scale is sufficiently reliable and valid for this purpose.

Certain education departments that did not use the OSAIS did not participate in the re-standardization. The scale was standardised on children of the education department of the former House of Representatives and the former Free State, Natal and Transvaal education departments. Although the scale was standardised for this population, it can probably also be used for children whose mother tongue is English or Afrikaans and who were not under the jurisdiction of the education departments mentioned at the time of the standardization. However, the validity and reliability of ISGSA scores obtained for such children have not yet been established.

Norms

The ISGSA is no longer an age scale like the OSAIS, but a point scale with deviation scores. The raw score total obtained by the testee is converted to the deviation score, the SA score, with a mean of 100 and a standard deviation of 15. The raw score total can also be converted to a test age in years and months.

Both types of norms are given for two norm groups, namely (a) a proportionally constituted norm group that includes environmentally disadvantaged and non-environmentally disadvantaged children, and (b) a non-environmentally disadvantaged norm group. The SED questionnaire is used to determine whether the testee is environmentally disadvantaged or not, and the appropriate norm group is determined according to this result.