“…In comparative studies, reported sample means for CA ranged from 31 to 144 months (Hellendoorn & Hoekman, 1992;Switzky, Ludwig, &c Haywood, 1979) and the range of mean MA was 27 to 90 months (Home & Philleo, 1942;Sigman &c Ungerer, 1984). Given the developmental progression of play skills (Fein, 1981;Rubin et al, 1983) and behavioral differences in play among typical children due to age (e.g., Elder &c Pederson, 1978;Fein &c Apfel, 1979;Lunzer, 1959;Moller & Rubin, 1987;Overton &c Jackson, 1973;Tizard et al, 1976a;Vandenberg, 1981), caution should be used in interpreting outcomes across studies using participants who differ on CA. This is especially true with respect to studies in which considerable variability in CA is evident within a study sample.…”