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Field
Randomization Method
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Before
Randomization is done in office using Stata 18.5 based on the baseline data we collected. We initially registered an individual randomization stratified by class. After collecting the baseline data, we observed a low ICC of 0.01052 at class level, which allowed us for a cluster randomization (MDEs of individual and clustered randomization are qualitatively similar). We thus updated our power calculations below and randomized 70 classes (instead of individuals) into control, treatment 1 and treatment 2 stratified by school. This change in randomization approach is meant to better guard against spillovers and make administration of vouchers easier. After randomizing classes into three groups, we checked balance on the meal choice (primary outcome), as well as age, BMI for age, weight, height and class size. We detected no significant differences at conventional levels.
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After
Randomization is done in office using Stata 18.5 based on the baseline data we collected. We initially registered an individual randomization stratified by class. After collecting the baseline data, we observed a low ICC of 0.01046 at class level, which allowed us for a cluster randomization (MDEs of individual and clustered randomization are qualitatively similar). We thus updated our power calculations below and randomized 70 classes (instead of individuals) into control, treatment 1 and treatment 2 stratified by school. This change in randomization approach is meant to better guard against spillovers and make administration of vouchers easier. After randomizing classes into three groups, we checked balance on the meal choice (primary outcome), as well as age, BMI for age, weight, height and class size. We detected no significant differences at conventional levels.
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Field
Sample size (or number of clusters) by treatment arms
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Before
The targeted 1011 baseline participants in 70 classes in 5 schools are allocated to the three groups in a roughly balanced way (stratified by schools): 327 students (23 classes) in control group, 342 students (23 classes) in treatment 1 (restricted voucher) and 342 students (24 classes) in treatment 2 (voucher with choice).
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After
The targeted 1011 baseline participants in 70 classes in 5 schools are allocated to the three groups in a roughly balanced way (stratified by schools): 328 students (23 classes) in control group, 337 students (23 classes) in treatment 1 (restricted voucher) and 346 students (24 classes) in treatment 2 (voucher with choice).
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