Social experiments.
D000293:Adolescent; D000328:Adult; D002648:Child; D004812:Epidemiologic Methods; D005260:Female; D006266:Health Education; D006285:Health Planning; D006291:Health Policy; D006302:Health Services Research; D006801:Humans; D007223:Infant; D008297:Male; D009310:National Health Insurance, United States; D011897:Random Allocation; D012107:Research Design; D012572:School Health Services; D012936:Social Medicine; D014481:United States