Sampling Methods

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Random Sample

Each member of the target population has the same chance of being selected

Can be done by putting the names of every member of the target population in a hat or using a randomising programme

The choice is not biased on the part of the researcher

Very rarely used as compiling a list of the target population is very time consuming or even impractical for a very large target population

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Stratified Sample

Involves dividing the target population into subcategories and selecting members of each subcategory in the proportion that they occur in the target population

Might be more representative as an effort is made to identify the important characteristics of the target population and ensure that they are represented in the sample

Can be very time consuming as each relevant category in the target population has to be identified and their proportion calculated

Provides the best chance of obtaining an unbiased and representative sample

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Opportunity Sample

Involves selecting the participants available at the time the research takes place

Quick and convenient therefore the most economical. It is the most often used sampling method

Unrepresentative of the target population and biased

Can be biased on the part of the researcher who may choose the ppts most likely to be helpful

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Volunteer Sample

Involves using ppts who choose to be part of the study. Can be recruited by newspaper advertising.

Convenient and ethical as people choose to be involved

Unrepresentative of the target population

The choice isn't biased on the part of the researcher