Sampling

1
Sampling
General population
General population
Target population
Target population
Sample
Sample
?
2
Sampling

• Researchers aim to get a sample that is
  representative of the target population
• Every type of person in the TP should be
  proportionally represented in the sample
• NB it is not necessary for the sample to be
  representative of the GP unless the researcher
  intends to generalise

3
Sampling

• Opportunity sampling
• Use whoever is immediately available e.g. go out
  and accost passers-by
• Volunteer sampling
• Use whoever puts themselves forward e.g.
  advertise in the paper

4
Sampling

• Quota sampling
• Design a sample to reflect the TP and then
  recruit to order
• Random sampling
• Every member of the target population has an
  equal chance of being selected
• E.g. selected by computer from the electoral roll

5
Sampling

• random

• random

• quota

• quota

How difficult to obtain

• opportunity

• opportunity

• volunteer

• volunteer

How likely to be representative