Sampling

• define population

  -a group of people who are the focus of the researchers interest, from which a smaller sample is drawn.
• define sample

  -a group of people who take part in a research investigation. The sample is drawn from a target population and is presumed to be representative of that population.
• define representativeness

  -the extent to which a sample mirrors a researcher's target population and reflects its characteristics.
• How to carry out random sampling

  -A researcher gathers a list of all members of the target population.

  -All names are given a number. ​

  -Numbers are then randomly chosen (out of a hat, using a number generator etc.) until researchers get their desired sample size.

  -All members of a target population have an equal chance of being selected.
• systematic sampling

  -When every nth member from the target population is selected.

  -A researcher gathers a list of all members of the target population (sampling form).​

  -Every 5th name on the list is selected for the sample. ​

  -Researchers do this until the sample is complete.
• stratified

  -A sample that reflects the proportion of certain characteristics in the target population. Members of the sample are randomly selected.
• outline the procedure in stratified sampling

  -Researcher identifies the different types of people that make up the target population. ​

  -They work out the proportions of each type of person within the group (work out relative %)​

  -The sample then must contain these groups in the same proportion as the target population.​

  -Ppts will be randomly chosen from the relative group.
• an example of stratified is

  -If 40% of the researcher’s target population is female, then 40% of their sample must also be female.
• volunteer sampling

  -When a person from the target population selects themselves for participation.​​

  -A researcher puts an advertisement out (post online, in newspaper etc.) outlining their ideal participants.​

  -People are able to self – select, contact researcher and volunteer.
• opportunity sampling

  -Researcher selects any ppt from the target pop that is available at the time
• strength of random

  Avoids bias.
• weaknesses of random

  -Difficult and time consuming. ​

  -May still end up with unrepresentative sample.
• strengths of systematic

  -Avoids bias. ​

  -Can be quite representative.
• weakness of systematic

  -Difficult to achieve due to it being time consuming and costly.
• strengths of stratified

  -Produces a representative sample

  -highly generalisable.
• weakness of stratified

  -This would be extremely time consuming and difficult to do. It’s rarely used in Psychology.
• strengths of opportunity

  -Quick and easy method.
• weakness of opportunity

  -Might not generate a representative sample.​

  -Could be biased.
• strengths of volunteer

  -Quick, easy, convenient.
• weakness of volunteer

  -Bias: the type of person who volunteers e.g., an TV ad at lunchtime will only produce ppts who do not work full time.