Table 4.

Estimated difference-in-difference (DID) average number of entrées served, share of entrées served with vegetables, fruit and milk, and à la carte sales per day for a study assessing two interventions (Healthy Choices and Healthy Nudging) to increase meal participation in high schools. Data for these models were obtained daily from school cafeteria registers in three Northeast US high schools participating in the study during the 2013–2014 school year. All students in all three schools were eligible for free/reduced-price school meals under the US Department of Agriculture Community Eligibility Provision

	DID estimators† reported with 95 % heteroscedastic-robust se
	Average number entrées served daily	se	Average number of cold entrées served daily	se	Average number of hot entrées served daily	se	Average share of entrées served with a vegetable daily	se	Average share of entrées served with a fruit daily	se	Average share entrées served with a milk daily	se	Average competitive foods sold daily‡	se
Healthy Choices School	82·050*	33·898	69·655**	21·954	11·304	28·545	0·060**	0·020	−0·067	0·039	−0·060	0·042	–§	–
Healthy Nudging School	107·431**	28·196	52·820*	22·406	54·333*	24·411	0·036	0·034	0·054	0·059	−0·004	0·044	13·85	19·06
Number of days	332		332		332		332		332		332		225

*P < 0·05, **P < 0·01.

^†DID estimates calculated using multiple linear regression as: DID estimate = [average intervention (post) – average intervention (pre)] – [average comparison (post) – average comparison (pre)]. Models included covariates controlling for seasonal variation in school meal participation with a month fixed effect, and binary dummy variables for the type of entrée served each day. Robust se were used to account for heteroscedasticity.

^‡Total competitive foods sold excludes pretzels, ice creams and mozzarella sticks.

^§Competitive foods were completely removed from the Healthy Choices School; therefore, DID estimates were not obtained.