Table 2.

Psychometric properties of the Internet Gaming Disorder Scale – Short Form (IGDS-SF) in item level

Item no.	Analyses from classical test theory			Analyses from Rasch
	Factor loadingsa	Item–total correlation	Test–retest reliabilityb	Infit MnSq	Outfit MnSq	Difficulty	DIF contrast across genderc,d	DIF contrast across time on gamingc,e
IGDS-SF1	0.68	0.63	0.80	1.08	1.05	1.57	−0.02	−0.10
IGDS-SF2	0.80	0.74	0.83	0.79	0.74	1.42	0.30	0.14
IGDS-SF3	0.77	0.72	0.87	0.83	0.77	−0.17	0.11	−0.07
IGDS-SF4	0.56	0.54	0.84	1.37	1.34	0.26	−0.55	−0.67
IGDS-SF5	0.79	0.74	0.79	0.79	0.86	−0.46	0.09	0.34
IGDS-SF6	0.69	0.65	0.83	1.01	1.00	−0.29	0.07	−0.15
IGDS-SF7	0.63	0.60	0.91	1.15	1.06	−0.54	−0.22	−0.35
IGDS-SF8	0.77	0.72	0.88	0.84	0.80	−0.73	0.21	0.23
IGDS-SF9	0.66	0.62	0.79	1.16	1.17	−1.06	0.00	0.61

Note. MnSq: mean square error; DIF: differential item functioning.

^aBased on confirmatory factor analysis. ^bUsing Pearson’s correlation. ^cDIF contrast >0.5 indicates substantial DIF. ^dDIF contrast across gender = difficulty for females − difficulty for males. ^eDIF contrast across time on gaming = difficulty for participants with median weekly hours or below on gaming (i.e., ≤19 hr) − difficulty for participants with above median weekly hours on gaming (i.e., ≥20 hr).