Sampling Methods - Research Methods

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Volunteer Sampling

people who have chosen to take part in the study (also known as self-selecting)

Example: people who respond to an advert for participants


  • relatively convenient and ethical if it leads to informed consent
  • reduces researcher bias by not choosing participants


  • unrepresentative - leads to participant bias (e.g. a daytime TV advert would not attract full time workers)
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Opportunity Sampling

selecting people available at the time

Example: going up to a person in a cafe and asking them to be interviewed


  • Quick and conveneient (most commonly used type)


  • very unrepresentative samples and often biased by researcher choosig those who appear most helpful
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Random Sampling

Every member of the target population has an equal chance of being selected

Example - pulling names from a hat


  • For very large samples it provides the best chance of an unbiased, representative sample


  • Not always ensure an unbiased sample is chosen - for example all girls may be randomly pulled from the hat
  • Time consuming creating a list of names in a large population
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Stratified Sampling

Dividing target population into important subcategories and selecting members in proportion to the way they occur in the subcategories

Example - 60% of the population are females so 60% of the sample are female


  • deliberate attempt to make the sample representative


  • can be time consuming as subcategories and proportions have to be identified
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Systematic Sampling

taking every nth person on a list to create a sample

Example - taking every fourth person


  • unbiased selection increasing chances of unbiased and representative sample (no researcher bias)


  • not always representative - may end up selecting all females
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