Improving IQ measurement in intellectual disabilities using true deviation from population norms

Table 3 Summary of hierarchical regression analyses

Criterion score	Step	Scale	r	Finalβ	R ²	ΔR²
Vineland composite	1	FSIQ	.48	.19	.23
	2	+ FSIQ z-score	.51	.35	.26	.03^a
	1	EXIQ	.48	.13	.22
(n = 279)	1	EXIQ	.48	.13	.22
(n = 279)	2	+ FSIQ z-score	.51	.39	.25	.03^a
Vineland communication (n = 279)	1	VIQ	.49	.27	.24
Vineland communication (n = 279)	2	+ VIQ z-score	.50	.29	.27	.03^a
PPVT (n = 184)	1	VIQ	.67	.32	.45
PPVT (n = 184)	2	+ VIQ z-score	.69	.43	.51	.06^a
Raven (n = 173)	1	NVFRSS	.57	.07	.32
	2	+ NVFR z-score	63	.58	.40	.08^a

^aP < .001; r = correlation between predictor and criterion variable.
EXIQ, Extended IQ; FSIQ, Full Scale IQ; NVFRSS, Non-verbal Fluid Reasoning Standardized S core; VIQ, Verbal IQ; PPVT, Peabody Picture Vocabulary Test.

ISSN: 1866-1955