Statistics/Methods of Data Collection/Sample Surveys

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Sample surveys involve the selection and study of a sample of items from a population. A sample is just a set of members chosen from a population, but not the whole population. A survey of a whole population is called a census.

Examples of sample surveys:

• Phoning the fifth person on every page of the local phonebook and asking them how long they have lived in the area. (Systematic Sample)

• Dropping a quad. in five different places on a field and counting the number of wild flowers inside the quad. (Cluster Sample)

• Selecting sub-populations in proportion to their incidence in the overall population. For instance, a researcher may have reason to select a sample consisting 30% females and 70% males in a population with those same gender proportions. (Stratified Sample)

• Selecting several cities in a country, several neighbourhoods in those cities and several streets in those neighbourhoods to recruit participants for a survey (Multi-stage sample)

The term random sample is used for a sample in which every item in the population is equally likely to be selected.