Pew Research Center designed this study to assess the current state of online survey sampling methods – both probability-based and opt-in – and determine their accuracy on general population estimates ...

The study of hard-to-reach populations presents significant challenges. Typically, a sampling frame is not available, and population members are difficult to identify or recruit from broader sampling ...

verybody has a favorite color and season—preferences that seem innate, always defying reason. Auditors are no different when it comes to haphazard sampling, a process in which—ideally—they choose ...

This is a preview. Log in through your library . Abstract Background: Estimating the sizes of populations at highest risk for HIV is essential for developing and monitoring effective HIV prevention ...