Table 4. Item Response Theory Parameters for Items With Suspected DIF by Sex.

Module, construct, and item	a	b 1	b 2	DIF type	R 2	∆β	ESSD	ETSSD	UETSDS
Module 1.1, RRB, hand mannerisms
Male	0.91	−3.03	−1.03	Nonuniform	0.01	0.01	−0.45	0.01	0.18
Female	1.15	−1.82	−0.41
Module 1.2, SA, facial expressions
Male	2.31	−0.89	1.43	Nonuniform	0.01	0.01	0.03	<0.001	0.07
Female	1.93	−1.42	1.37
Module 2.1, SA, unusual eye contact
Male	1.51	−0.42		Nonuniform	0.001	0.001	−0.03	−0.12	0.61
Female	2.77	−0.38
Module 2.1, RRB, hand mannerisms
Male	1.18	−1.06	1.18	Nonuniform	0.03	0.001	−0.66	NA	NA
Female	0.94	−0.67	0.94
Module 2.2, RRB, hand mannerisms
Male	2.23	−0.84	0.32	Nonuniform	0.01	0.01	−0.64	−0.10	0.59
Female	1.94	−0.61	0.73
Module 3, SA, gaze
Male	3.53	0.00	1.34	Uniform	0.003	0.001	0.15	−0.04	0.20
Female	3.04	−0.12	1.34
Module 3, SA, initiation of joint attention
Male	1.13	−0.01	2.22	Uniform	0.002	0.006	−0.26	NA	NA
Female	0.95	0.33	2.85
Module 3, RRB, hand mannerisms
Male	0.87	0.12	2.00	Uniform	0.02	0.04	−0.55	NA	NA
Female	0.98	0.55	2.46

Abbreviations: a, item discrimination; b, item difficulty for each level of response; DIF, differential item functioning; ESSD, expected standardized score difference; ETSSD, expected test standardized score difference; NA, not applicable; RRB, repetitive, restrictive behaviors; SA, social affect; UETSDS, unsigned expected test score difference in the sample.