Stratified random sampling is a method of sampling that divides a population into smaller groups that form the basis of test ...

A simple random sample is a subset of a statistical population where each member of the population is equally likely to be ...

Note: This report was updated on Dec. 30, 2015 to reflect the January-July 2015 National Health Interview Survey estimates released on December 1, 2015. Telephone surveys face numerous challenges, but ...

Part One: The nature and process of social research ; Social research strategies ; Research designs ; Planning a research project and formulating research questions ; Getting started: Reviewing the ...

Pew Research Center’s international surveys are largely conducted via telephone or face-to-face interviews, depending on the country. (The exceptions are the United States and Australia, where surveys ...