Revised Knox Preschool Play Scale: interrater agreement and construct validity.

OBJECTIVE Interrater agreement and construct validity of the Revised Knox Preschool Play Scale (RKPPS) were examined. METHOD Two separately trained raters evaluated 38 typically developing children, ages 36 to 72 months. For each child, the raters observed two 15-min free-play sessions. RESULTS For the overall play age, the scores of the two raters were within 8 months of each other 86.8% of the time; for the 4 dimension scores, they were within 12 months of each other 91.7% to 100% of the time; and for the 12 category scores, they were within one age level of each other 81.8% to 100% of the time. Construct validity results showed a general match between the children's chronological ages and their overall play age scores. CONCLUSIONS Findings suggest that two raters can score the RKPPS with some consistency and that scores on this measure progress developmentally, thus supporting its construct validity.