For all our projects we use face-to-face interviews (PAPI, CAPI) or telephone interviews (CATI). Interviews are conducted using structured and pretested questionnaires. A combination of stratification and cluster sampling is used to obtain a nationally representative samples. For each country, all regions are included in the sample frame and have a possibility of selection. Data entry and processing is carried out using specialized software.
Sample sizes are sufficient to extrapolate the results to the general population. Typically all our population surveys are conducted with samples of 1,000 to 1,500 interviews per country.
To ensure the highest quality of data, we implement a rigid quality control system. Quality control procedures include direct observations by supervisors, back checks by phone, post-field review of audio files. All completed interviews are subject to logical control for proper administration prior to data entry. Additionally, 100% of cases were subject to back check via GPS control.