Complex Surveys Components of a complex survey random

Complex Surveys • Components of a complex survey: random sampling; ratio estimation; stratification; clustering. • How to assemble above components into a complex survey?

Malaria in Gambia • Malaria occurs in over 100 countries. More than 40% of the people in the world are at risk. • Malaria kills about 2 million people annually, mostly African children under the age of 5. • Malaria is a serious health problem in Gambia. • Malaria is transmitted by mosquito. • Malaria morbidity can be reduced by using bed nets that are impregnated with insecticide.

Nationwide Survey on the Prevalence of Bed Net Use in Rural Areas (1991) • Sampling frame: all rural villages of fewer than 3000 people Stage Sampling Unit Stratification Sampling Probabilities Proportional to district population Proportional to village population 1 District Region 2 Village PHC/non. PHC 3 Compound Random sampling

Estimating a Distribution Function • Historically, sampling theory was developed to answer questions like “What percentage of adult males are unemployed? ” or “What is the total amount of money spent on health care in the United States? ” or “What is the ratio of the numbers of exotic to native birds in an area? ” • But Statistics other than means or totals may be of interest. For example, you may want to see the distribution of the midterm scores.