Book excerpt: Basic model of sampling from a population with identifiable units; Inference under the fixed population model: the concepts of sufficiency and likelihood; inference under the fixed population model: criteria for judging estimators and strategies; Inference under superpopulation models: design-unbiased estimation; Inference under superpopulation models: prediction approach using tools of classical inference; Inference under superpopulation models: using tools of bayesian inference; Efficiency robust estimation of the finite population mean.