The document discusses improving data quality in surveys. It covers topics like non-response bias, questionnaire design, question construction, and pre-testing. To address non-response bias, the document recommends documenting non-responses, looking for correlations with response rates, using incentives thoughtfully, and gathering information from interviewers about non-respondents. For best questionnaires, it suggests starting with clear objectives, following good design practices, crafting clear questions informed by research, and pre-testing surveys. The overall goal is to reduce errors and biases to improve the reliability and validity of survey data.