Term
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Definition
| Sample: chosing people in the particiapant. |
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Term
Random sample:
Every member of the target population has an equal change of being selected (either by drawing names from hat or using random numbers table/software) |
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Definition
Advantages: Theoretically ,this is the most likely way of producing a represation sample (but a larger sample size is required). Unaffected by experiment bios.
Disadvatages: In practical, very difficult to achieve, especially if sample size is (relatively) small). |
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Term
Opportunity sample:
Selecking/asking the first people who come along, or using a ready-made group of people (such as fellow students or your family). |
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Definition
Advantages: Cheap, easy, convenient and quick.
Disadvantages: You can't be sure it is representative - although this will depend on what your stated population is. |
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Term
Quota sample:
The selected sample comprises specified groups in proportion to the target population
Example: from the target population of 100 female and 60 male, a quota sample might contain 20 female and 12 male. |
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Definition
Advantages: This is likely to be a representative sample, thus allowing generalization.
Disadvantages: In itself, it isn't a random sample, this makes it more difficult to be sure of its representativeness. Can be consuming and costly. |
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Term
Stratified sample:
The researcher identifies the different groups in target population, then, as in quota sampling, an appropriate number is selected from each group, but this is done randomly |
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Definition
Advantages: As a combination of random and quota sampling, it is likely to produce a representative sample, thus allowing generalization.
Disadvantages: Can be time-consuming and costly. |
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Term
Systematic sample:
Every nth person is selected from the list.
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Definition
Advantages: Unaffected by experimenter bios.
Disadvantages: May not be representarive. Depending on how the list is arranged, there may be an over-representation of one or more groups relative to others. |
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Term
Self-selecting (voluteer) sample:
Volunteers respond to an advertisement for participation in a study. |
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Definition
Advantages: Once the advert has been placed, it is a quick and easy way of recruiting participants.
Disadvantages: The volunteers can only be reprentative of those who saw the advert in the first place (e.g. readers of a particular newspaper/ magazine). Even then, volunteers may differ from non-volunteers in important ways. |
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