DHS surveys collect primary data using several types of questionnaires. The Household Questionnaire is used to gather information on household composition, the characteristics of the dwelling, and other household-level indicators. It also includes a biomarker, which collects data on eligible household members, such as height, weight, hemoglobin levels, dried blood samples for HIV testing, and other country-specific health indicators. In addition, the Household Questionnaire serves to identify eligible women and men who will be selected for individual interviews using the Women's and Men's Questionnaires.