Converting Shipley Institute of Living Scale scores to IQ: a comparison of methods

A sample of 486 male veteran psychiatric patients at a Veterans Administration medical center were used to compare five different methods of estimating IQs from Shipley Scale scores. The methods were: (1) Grayson VA norms; (2) Paulson and Lin Table 5; (3) age-corrected Paulson and Lin Table 4; (4) Zachary et al. continuous age norms; and (5) Tamkin and Jacobsen method applying age-correction to Paulson and Lin's Table 5. An intercorrelation matrix, mean, standard deviation, and range were computed for all five IQ estimates. The same analyses were computed separately by age decade. The results suggest the advisability of using age-corrected norms for estimating IQ from the Shipley Scale. Norms uncorrected for age result in underestimates for older subjects. The Zachary et al. and Tamkin and Jacobsen methods yielded highly similar results.