Describe some of the criteria involved in selecting a representative sample.
The selection of a representative sample involves two main criteria. First, the relevant strata in the population must be identified before selection. For example, when researching attitudes towards trade unions, it is important to consider workers, managers, and industrialists as separate strata.
Second, the actual unit—whether a person, household, or village—should be chosen purely by chance. This principle is called randomisation. Being selected in the sample should be a matter of luck, like winning a lottery. If a survey team chooses only villages near the main highway or mostly middle-class households they know, the sample becomes purposive rather than representative. Additionally, the size of the sample matters—the bigger the sample, the more chance it has of being truly representative.
Explanation
The textbook context clearly outlines the criteria for selecting a representative sample. The first principle is identifying relevant strata in the population (stratification). The second principle is randomisation—selection based purely on chance. The context also mentions that sample size affects representativeness, and the mode of selection is even more important than size. The context warns against purposive samples where selection is based on convenience or bias (like choosing villages near highways or known households).