Methods of sampling - introduction
When designing a sample the firm needs to consider:
- The sample frame - a complete list of all people or households in the target population from which the sample is drawn.
- The sample size - the number of people to include in the survey
It is normally accepted that the larger the sample size as a proportion of the sample frame, the more likely it is to represent the characteristics of the total population. So, if a firm can afford a larger sample, it is likely to produce more reliable results. Once it has decided on the size of sample size, a method must be chosen to select the sample.
Let's consider an example of a market - a school. Assume that there are 2,000 pupils, 45% of which are boys. The age range is from 11 to 18, and there is an approximately even distribution of ages. The school is split into 7 year groups, again of approximately equal sizes. If we wish to do research here we will need to take samples.