As an estimator of the population mean, the sample mean based only on the distinct units possesses a remarkable invariance property. Under three forms of simple random sampling, viz. simple random ...

When observations are costly or time-consuming but the ranking of the observations without actual measurement can be done relatively easily, rankedset sampling (RSS) can be employed instead of simple ...

A statistically designed random sampling scheme, based on as few as 100 people, would give a very high probability of detecting if there are any COVID-19 cases and highlight at-risk hotspots.