The random sample survey is a commonly used method in market research and such surveys generally are considered to provide more robust results than purposive or convenience (such as quota) samples.

In the case of studies where sample units are clusters, each unit is qualitatively classified into one of several groups according to some characteristic, and the ultimate units of observations are ...

Consider a population in which the variable of interest tends to be at or near zero for many of the population units but a subgroup exhibits values distinctly different from zero. Such a population ...

To calculate intra-cluster and intra-household design effects and intra-class correlation coefficients for dietary nutrients obtained from a 24 h record-assisted recall. There were 125 children in 50 ...