Sampling

• Opportunity sampling consists of taking the sample from people who are available at the time the study is carried out.

  + convenient

  + no need to divide population into strata

  _ unrepresentative of target population - cant be generalised

  _ researcher has complete control over selection (researcher bias)
• Random sampling is where every member of the target population has an equal chance of being chosen.

  + potentially unbiased enhancing internal validity

  _ selected participant may refuse to take part

  _ Difficult and time-consuming to conduct
• Volunteer sampling consists of p's volunteering when asked or in response to an advert.

  + easy as minimal input from researcher

  + Participants more engaged

  _ demand characteristics
• Systematic sampling is where every nth member of the target population is selected.

  + Objective as researcher has no influence over who is chosen

  _ time consuming

  _ Participants may refuse to take part
• Stratified sampling is where the composition of the sample proportionally represents the subgroups within the target population.

  + Produces a representative sample so findings can be generalised

  _ Identified strata can't reflect all ways people are different so complete representation isn't possible