Usefulness of the Slosson Intelligence Test with Severely and Profoundly Retarded Children

Abstract

The passage of Public Law 94-142 has increased the use of brief psychometric devices by special educators of the severely and profoundly mentally retarded for routine retesting purposes. Unfortunately, there is a need for studies of reliability and validity of these norm-referenced psychometric devices. One such brief intellectual screening test is the Slosson Intelligence Tesc. Correlations of scores on the Slosson Intelligence Test and Stanford-Biner IQs of mentally retarded individuals have yielded values ranging from .GO to .94 (1, 3). A review (2) reported that, when the intelligence range is not restricted, the correlations between scores on the Slosson and the Stanford-Biner rend to be high, whereas when the range is restricted, correlations are lower. This study assessed the concurrent validity of the Slosson Intelligence Test when administered to 40 severely and profoundly mentally retarded school children by special educators. All subjects had been tested by certified psychologists with the Stanford-Binet prior to the study. The children, who ranged in age from 11.3 to 19.9 yr. (M 15.5, SD 2.1), .were administered the Slosson Intelligence Test by five special education teachers enrolled in a graduate course on diagnostic assessment The teachers were taught to administer and score the test by the first author. Each observed the author during two demonstrations. The mean IQs and standard deviations were for the Slosson 26.78 and 15.75; for the Binet 24.85 and 16.74. IQs on the Slosson ranged from 4 to 55, whereas IQs on the Stanford-Binet ranged from 8 to 45. Slosson IQs were larger than Stanford-Binet IQs for 30 of the 40 childrem; four students had Slosson IQs 7 or more points higher than their Stanford-Binet IQs. The distribution of IQs was bimodal and skewed towards 5 and 35. A Pearson product-moment correlation of .90 was obtained for raw scores. The correlation suggests high agreement in the ranking of the srudents tested. However, the skewness of the present distribution and the similar nature of the tests inflate the obtained validity. These observations demand cautious use of IQs from the Slosson Intelligence Test.