Chapter 2: Sample Selection

Sampling methods are categorized into two main groups as probable and non-probable sampling methods. Probable sampling methods are methods in which the subjects are known from the population and can be selected with equal probability. They are categorized into four groups as follows:

In simple random sampling, all individuals in the population are listed and numbered. Then, the individuals selected in the sample are selected by using the “Random Numbers Table.”

Stratified sampling method should be used when there is heterogeneity between strata and homogeneity within strata. If the studied variable differs according to any characteristic of the individuals in the population, such as education, age, gender, and socioeconomic level, then the individuals in the population should be stratified according to this characteristic first. Then, enough subjects from each stratum should be selected by simple random sampling method.