Census and sample

Because of the cost and time required, it is not usually possible to collect data from every individual of interest. Sufficiently accurate information can often be obtained from a subset of this population — a sample.

Simple random sample

The simplest way to select a representative sample from a population is called a simple random sample. In this, each unit has the same chance of being selected. Some random mechanism (e.g. tossing a coin, rolling a die or a computer-based method) is used to determine whether any particular unit is included in the sample.

Illustration of random samples