Sample-size implications for population-based cluster surveys of nutritional status

We studied the design effects for population-based surveys that estimated the prevalence of wasting and stunting malnutrition in Malawi, Zambia, Indonesia, and Nepal, and studied the magnitude of different types of malnutrition clustering within villages. Weight, height, and midupper-arm circumference were measured on all children or on systematic samples of children in randomly selected villages. Design effects ranged from 0.53 for low height-for-age in Zambia to 6.12 for low weight-for-age in Nepal. If all sampled clusters were of size 30, as is often the case for nutrition surveys, design effects would have ranged from 0.44 for low height-for-age in Zambia to 2.59 for low midupper-arm circumference in Zambia. Malnutrition did cluster within villages. Stunting malnutrition clustered less than did wasting malnutrition. Nutrition surveys using clusters of 30 can sample fewer clusters than currently recommended if basic prevalence and cluster information are available prior to sample selection.