Self efficacy for fruit, vegetable and water intakes: Expanded and abbreviated scales from item response modeling analyses

Baranowski, Tom; Watson, Kathleen B; Bachman, Christine; Baranowski, Janice C; Cullen, Karen W; Thompson, Debbe; Siega Riz, Anna-Maria

doi:10.1186/1479-5868-7-25

International Journal of Behavioral Nutrition and Physical Activity

Table 1 Results from Classical Test Theory and Item Response Modeling Analyses of the Fruit Self-Efficacy Scales

From: Self efficacy for fruit, vegetable and water intakes: Expanded and abbreviated scales from item response modeling analyses

Scale/Item			M (SD)	CITC	Factor	Est (SE)	Infit
Item stem for Fruit (N = 664): How sure are you that you can...
181	×	eat 1 portion of fruit for a snack at home at least one time?	0.82 (0.38)	0.47	0.70	-0.94 (0.07)	0.94
169		drink a glass of 100% juice or eat a piece of fruit at breakfast at least one time?	0.78 (0.40)	0.42	0.63	-0.64 (0.07)	0.97
173	×	eat 1 portion of fruit at lunch at least one time on a school day?	0.78 (0.41)	0.43	0.64	-0.63 (0.07)	1.00
197		eat 1 portion of fruit at a cafeteria place at least one time?	0.77 (0.41)	0.49	0.70	-0.56 (0.07)	0.92
165		ask someone in family to buy your favorite fruit or vegetable at least one time?	0.77 (0.41)	0.43	0.63	-0.56 (0.07)	1.02
187	×	eat 1 portion of fruit for dinner or supper at home at least one time?	0.77 (0.42)	0.43	0.63	-0.49 (0.07)	1.00
177	×	eat 1 portion of fruit for lunch at least one time on a non-school day, including weekend?	0.75 (0.43)	0.41	0.60	-0.39 (0.07)	1.01
185		ask someone in family to serve 1 fruit instead of usual dessert for dinner at least 1 time?	0.75 (0.43)	0.48	0.68	-0.36 (0.07)	0.95
182	×	eat 1 portion of fruit for a snack at home at least 4 days a week?	0.72 (0.44)	0.48	0.68	-0.22 (0.07)	0.93
174		eat 1 portion of fruit at lunch most school days?	0.71 (0.45)	0.45	0.65	-0.11 (0.07)	1.01
178	×	eat 1 portion of fruit for lunch most non-school days, including weekends?	0.69 (0.46)	0.47	0.66	-0.02 (0.07)	0.93
198		eat 1 portion of fruit most times when you eat at a cafeteria?	0.68 (0.46)	0.42	0.60	0.04 (0.32)	1.03
193	×	eat 1 portion of fruit at a fast food place at least one time?	0.67 (0.47)	0.39	0.54	0.15 (0.07)	1.04
170		drink a glass of 100% juice or eat a piece of fruit at breakfast at least 4 days a week?	0.66 (0.47)	0.47	0.66	0.17 (0.07)	0.97
167	×	ask someone in family to buy 3 fruit or vegetables at least one time?	0.66 (0.47)	0.33	0.47	0.21 (0.07)	1.12
189		eat 2 portions of fruit at least 4 days a week?	0.65 (0.48)	0.50	0.69	0.27 (0.07)	0.95
186	×	ask someone in family to serve 1 fruit instead of your usual dessert/dinner most nights?	0.64 (0.48)	0.46	0.64	0.31 (0.07)	0.98
188		eat 1 portion of fruit for dinner or supper at home most nights?	0.61 (0.48)	0.42	0.57	0.49 (0.07)	1.03
166	×	ask someone in family to buy your favorite fruit or vegetable every week?	0.59 (0.49)	0.42	0.58	0.57 (0.07)	1.06
190		eat 2 portions of fruit at least 4 days a week, even when you are stressed?	0.57 (0.49)	0.46	0.64	0.70 (0.07)	0.95
168	×	ask someone in family to buy 3 fruit or vegetables every week?	0.54 (0.49)	0.39	0.54	0.90 (0.07)	1.09
194	×	eat 1 portion of fruit most times when you eat at a fast food place?	0.50 (0.50)	0.36	0.49	1.11 (0.07)	1.11
Item stem for Vegetables (n = 659): How sure are you that you can...
183	×	ask someone in family to serve 2 vegetables for dinner at least one time?	0.71 (0.45)	0.44	0.66	-0.79 (0.07)	1.01
199		eat 1 portion of vegetables at a cafeteria at least one time?	0.69 (0.46)	0.50	0.72	-0.70 (0.07)	0.92
179	×	cut up 1 portion of vegetables and eat it with a dip for a snack at least one time?	0.67 (0.47)	0.40	0.58	-0.58 (0.07)	1.00
175		eat 1 portion of vegetables for lunch at least 1 time on non-school day, including weekend?	0.65 (0.47)	0.39	0.58	-0.46 (0.07)	1.12
171	×	eat 1 portion of vegetables at lunch at least one time on a school day?	0.63 (0.48)	0.43	0.63	-0.29 (0.07)	1.07
195		eat 1 portion of vegetables at a fast food place at least one time?	0.61 (0.48)	0.45	0.65	-0.18 (0.07)	1.05
184	×	ask someone in family to serve 2 vegetables for dinner most nights?	0.55 (0.50)	0.56	0.77	0.14 (0.07)	0.91
180		cut up 1 portion of vegetables and eat it with a dip for a snack at least 4 days a week?	0.55 (0.50)	0.39	0.56	0.15 (0.07)	1.09
176		eat 1 portion of vegetables for lunch for most non-school days, including weekends?	0.55 (0.50)	0.52	0.72	0.15 (0.07)	0.95
200	×	eat 1 portion of vegetables most times when you eat at a cafeteria?	0.52 (0.49)	0.54	0.75	0.36 (0.24)	0.97
172		eat 1 portion of vegetables at lunch at least 4 days a week at school?	0.50 (0.50)	0.53	0.73	0.44 (0.07)	0.98
191	×	eat 3 portions of vegetables at least 4 days a week?	0.50 (0.50)	0.56	0.76	0.47 (0.07)	0.91
196	×	eat 1 portion of vegetables most times when you eat at a fast food place?	0.49 (0.50)	0.50	0.70	0.49 (0.07)	1.05
192	×	eat 3 portions of vegetables at least 4 days a week, even when you are stressed?	0.44 (0.49)	0.55	0.76	0.81 (0.07)	0.95
Item stem for Water (n = 640): How sure are you that you can...
205	×	drink only water whenever you are thirsty for at least one day?	0.79 (0.40)	0.30	0.51	-0.78 (0.07)	1.10
202		drink 4 glasses or bottles of water at least 4 days a week?	0.77 (0.41)	0.50	0.82	-0.59 (0.07)	0.93
201	×	drink 4 glasses or bottles of water at least one day?	0.75 (0.43)	0.42	0.73	-0.43 (0.07)	0.94
206	×	drink only water whenever you are thirsty at least 4 days a week?	0.71 (0.45)	0.31	0.52	-0.13 (0.07)	1.10
204	×	drink 6 glasses or bottles of water at least 4 days a week?	0.60 (0.49)	0.45	0.75	0.57 (0.07)	0.96
207		drink 6 glasses or bottles of water at least 4 days a week, even when stressed?	0.59 (0.49)	0.44	0.71	0.63 (0.17)	0.99
203	×	drink 6 glasses or bottles of water at least one day?	0.57 (0.49)	0.47	0.78	0.74 (0.07)	0.98

% Variance Explained for Fruit (Factor 1/Factor 2) (38.8%/7.5%)-Cronbach's alpha/Person-separation reliability (full scale = 0.86/0.82; reduced scale = 0.75/0.74)
% Variance Explained for Vegetables (Factor 1/Factor 2) (47.1%/9.5%)-Cronbach's alpha/Person-separation reliability (full scale = 0.84/0.83; reduced scale = 0.70/0.76)
% Variance Explained for Water (Factor 1/Factor 2) (48.7%/20.3%)-Cronbach's alpha/Person-separation reliability (full scale = 0.77/0.66; reduced scale = 0.55/0.61)
Mean (M); standard deviation (SD), corrected item-total correlation (CITC); item response modeling item difficulty estimate and standard error [Est (SE)], Infit statistic (acceptable range 0.75-1.33); Self efficacy item scale: not sure (0), sure (1); "x" identifies items used in the reduced scales

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ISSN: 1479-5868

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