We randomly selected 806 children under 6 years of age from 45 primary anganwadi (childcare) centres in Chandigarh, Punjab, India, that were chosen through multistage stratified random sampling.
在印度旁遮普省昌迪加尔的45所托儿所(anganwadi)中心采用多级分层随机取样法选择了806名6岁以下儿童。
Scientists believe the existence of this age-old reward mechanism indicates there is an evolutionary advantage in sampling the unknown.
科学家认为，脑部这种古老的奖励机制在尝试未知事物方面有进化优势。
Methods Questionnaire survey was conducted among 1298 residents sampled by randomly stratified sampling. The age of the residents ranged from 15 to 69 years old.
方法用分层随机抽样的方法抽取1298名15 ~ 69岁的农村居民进行问卷调查。
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