The factorial structure and specificity of the British Ability Scales


Department of Education, University of Manchester, Oxford Road, Manchester M13 9PL, UK.


Average correlations for three age groups from the BAS standardization data were factor analysed using principal-factor analysis. Children aged 5:0–7:11 years were given 19 scales, those of 8:0–13:11 were given 18, and those aged 14:0–16:11 were given 14. Two factors were extracted with eigenvalues > 1 at each age level. The first factor, clearly identifiable as g, accounted for about 30 per cent of the variance. The second factor, again clearly identifiable for each age group as verbal recall of pictures, accounted for between 5 and 9 per cent of the variance. The proportion of reliable specific variance was calculated for each scale, and this accounted for about 46 per cent of the variance. Well over half the reliable variance is therefore attributable to specificity. These results indicate higher levels of specificity than in the WPPSI, WISC-R and WAIS. It was concluded that the British Ability Scales have sufficient specificity to justify comparisons between scales in profiles of cognitive strengths and weaknesses.