The problem of estimating the variance of the ratio estimator in sampling with probability proportional to aggregate size is investigated. The form of nonnegative unbiased variance estimators is found ...

PROC SURVEYSELECT provides a variety of methods for selecting probability-based random samples. With probability sampling, each unit in the survey population has a known, positive probablity of ...

Why do pollsters make such a big deal about probability sampling? You'd think that choosing people to interview should be easy. Take three of these, four of those, and two of the other. But it's not.

The COVID-19 pandemic has infected over 38 million people around the world and is showing no signs of going away any time soon. Researchers worldwide are frantically working on developing an effective ...