Selection of observations taken from a subset of the population
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Sampling unit
Individual units of the population
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Sampling frame
Ordered list of sampling units
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Simple random sampling
Random sample in which every member has an equal chance of selection; RNG or lottery sample
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Advantages of simple random sampling
No bias; Easy + cheap for small populations and samples; Each sampling unit has known and equal chance of selection
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Disadvantages of simple random sampling
Not suitable for large populations and samples (time consuming); sampling frame needed
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Systematic sampling
Required members chosen at regular intervals from sampling frames; first chosen at random in the first interval;
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Advantages of systematic sampling
Suitable for large populations and samples; simple + quick to use
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Disadvantages of systematic sampling
Can introduce bias; sampling frame needed
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Stratified sampling
Population divided into strata and random sample taken from each; no sampled = (no in stratum / no in population) x overall sample size
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Advantages of stratified sampling
Sample accurately reflects the population structure; guarantees proportional representation of groups
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Disadvantages of stratified sampling
Population must be in strata; not suitable for large strata or large samples within each strata; sampling frame needed for each strata
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Quota sampling
Population divided into groups; proportion of groups to population should reflect groups in sample
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Advantages of quota sampling
Allows small sample to be representative of population; no sampling frame needed; quick, easy + cheap; allows for comparison between groups
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Disadvantages of quota sampling
Non-random so can introduce bias; population must be in groups (costly or inaccurate); increasing scope of study increases no of groups (time consuming + costly)
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Opportunity sampling
Taking sample from people who are readily available at the time and fit the criteria
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Advantages of opportunity sampling
Easy + inexpensive
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Disadvantages of opportunity sampling
Unlikely to be representative of population; dependent on researcher
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Other cards in this set
Card 2
Front
Observes every member of the population
Back
Census
Card 3
Front
Selection of observations taken from a subset of the population
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