Appendix A2.

Test statistics of the Differential Item Functioning analysis: Step 2

					Gamblers in the general population		Slot machine gamblers sample
Criterion	Hypothesis Test		G21	d.f.	a	b	a	b	μ	δ
1 Preoccupation	All	equal	10.7	2	0.82	−0.68	1.44	0.31	0.92	0.93
	a	equal	1.6	1	1.25	−0.54	1.25	0.23	0.9	0.99
	b	equal	9.2	1	0.96	−0.12	0.96	−0.12	0.84	1.04
2 Tolerance	All	equal	5.3	2	1.83	0.46	1.17	1.04	0.86	0.82
	a	equal	1.3	1	1.32	0.56	1.32	1.02	0.86	0.79
	b	equal	3.9	1	1.14	0.94	1.14	0.94	0.83	0.82
5 Gambling to escape	All	equal	3.4	2	0.83	1.71	0.79	1.1	0.92	0.79
8 Jeopardized matters	All	equal	3.2	2	2.2	1.48	1.84	1.19	0.99	0.88
9 Bail out	All	equal	2.7	2	2.42	1.9	1.26	2.25	0.91	0.84

¹Values exceeding 3.84 (the α = 0.05 critical value of the χ² distribution, when df = 1) are considered as significant difference (Thissen, 2001).