On Comparing Learning Disabled and Regular Classroom Children

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Abstract
Forty-seven studies, which compared normal and learning disabled children, were reviewed with a focus on the variability of performance within groups and the degree of overlap between LD and normal groups. The amount of variability of performance within LD and normal groups was similar and was approximately 75% of the variability of a randomly selected national sample. The average difference between the means of normal and LD groups was less than .75 SD, or about one sixth the range of performance which existed within either group. Assuming normal distributions, this means that more than 23% of the LD children scored above the mean of the normal group in most of the studies reviewed. On the basis of this data, it was asserted that categorical claims about the etiology or education of LD children were unwarranted and that combining LD and regular classroom groups has a relatively small effect on the range of ability in the classroom.