In science, a variable is something that can be changed, measured or controlled in an experiment. Scientists look at variables to understand how they affect things. A variable is any one of the things ...

When conducting surveys, two kinds of nonresponse may cause incomplete data files: unit nonresponse (complete nonresponse) and item nonresponse (partial nonresponse). The selectivity of the unit ...

An important part of the identification and diagnostic checking of space-time ARMA models is the evaluation of the significance of the autocorrelations of the observations and residuals, respectively.