The concurrent validity of the peabody individual achievement test and woodcock reading mastery tests among students with mild learning problems

Abstract

Previous research has revealed moderate to high validity coefficients between the Peabody Individual Achievement Test and the Woodcock Reading Mastery Tests. However, the same research has indicated rather consistently that the latter instrument provides significantly lower means than do several screening tests currently being used in the field. This investigation replicated and extended previous research by comparing the two instruments across three grade clusters in order to determine whether the lower Woodcock scores are equally robust for each level. As in prior research, validity coefficients were moderate to high in magnitude. However, the differences between the means of two instruments were found to decrease in size from earlier to later grades. That is, seven of the eight significantly different means were found to occur in grades 1 through 4. Only one significant difference was found for grades 5 through 8. Discussion sought to explain the results in terms of the representativeness of the Woodcock norms and the novel method that Woodcock used to estimate sample means and standard deviations.