An enire group of individuals. (but this can be impracical to examine all of them) Smaller groups of individuals selected from the populaion [a small sample can represent the enire populaion] Designed to ask quesions to a small group of people in the hope of learning something about the whole populaion (e. g. opinion polls) Sampling methods that tend to be over- or underemphasizing some characterisics of the populaion. [best way to avoid his is to sample at random] Protects from the inluences of all the features of the populaion. A parameter that is a part of a model for a populaion. Every sample of the size we want to draw has an equal chance to be selected. Each individual has an equal chance of being selected. Sampling frame: list of individuals from which the sample is drawn. : each draw of random numbers selects diferent people from our sample. These diferences lead to diferent values for the variables we measure.