. Author manuscript; available in PMC: 2018 Sep 13.

Published in final edited form as: Appl Res Qual Life. 2017 Apr 4;12(2):251–288. doi: 10.1007/s11482-017-9516-9

Table 9.

Feeling Tone Questionnaire (FTQ) positive affect item set: Differential item functioning (DIF) results. Race/Ethnicity subgroup comparisons

Item Description	IRTPRO		lordif		Magnitude (NCDIF)		Effect Size T1
Item Description	NHW vs. NHB	NHW vs. Hispanic	NHW vs. NHB	NHW vs. Hispanic	NHW vs. NHB	NHW vs. Hispanic	NHW vs. NHB	NHW vs. Hispanic
Positive affect item set
Are you feeling well?	U^*	U^*	NU	NU^*; U	0.0020	0.0116	0.0360	0.0794
Do you like being here?					0.0001	0.0015	−0.0107	−0.0254
Are you feeling happy today?	U^*	NU; U^*	U^*	NU; U^*	0.0076	0.0171	−0.0777	−0.1264^†
Are people helpful here?	U^*			NU	0.0036	0.0045	0.0540	0.0422
Do you have a good appetite?	U^*	NU; U^*	NU; U^*		0.0059	0.0019	0.0706	0.0287
Do you like the people here?	U^*			NU^*	0.0037	0.0024	0.0460	0.0321
Do you sleep well?	U^*	NU^; U^	U		0.0009	0.0067	−0.0293	−0.0174
Did you have a nice day yesterday?	U^*	NU; U			0.0007	0.0006	0.0136	−0.0167
Do you feel good about tomorrow?	U^*		U^*		0.0022	0.0006	−0.0464	0.0022

Asterisks indicate significance after adjustment for multiple comparisons.

^†

Indicates value above threshold of 0.10.

NU= Non-uniform DIF involving the discrimination parameters; U=Uniform DIF involving the location parameters.

For the lordif analyses, uniform and non-uniform DIF was determined using the likelihood ratio chi-square test. Uniform DIF is obtained by comparing the log likelihood values from models one and two. Non-uniform DIF is obtained by comparing the log likelihood values from models two and three. DIF was not detected using the pseudo R² measures of Cox & Snell (1989), Nagelkerke (1991), and McFadden (1974) or with the change in Beta criterion.