Table 3.

Quality assessment of studies included in a review of field experiments on the effectiveness of subsidies in promoting healthy food purchases and consumption

Item	Criterion of study quality	Mean	sd
1	A control group was included	0·60	0·50
2	Baseline characteristics between control and intervention groups were similar	0·25	0·44
3	The intervention period was at least 5 weeks	0·75	0·44
4	The follow-up period was at least 3 weeks	0·35	0·49
5	An objective measure of food purchases or intake was used	0·90	0·31
6	The measurement tool was shown to be reliable and valid in previously published studies	0·95	0·23
7	Participants were randomly recruited with a response rate of 60 % or higher	0·05	0·22
8	Attrition was analysed and determined not to differ significantly by respondents’ baseline characteristics between control and intervention groups	0·35	0·49
9	Potential confounders were properly controlled for in the analysis	0·50	0·51
10	Intervention procedures were documented in detail in the article	0·90	0·31
11	Total study quality score by summing up items 1 to 10	5·60	1·90

Note: Items 1 to 10 are all dichotomous variables.