sampling

• Cannot randomly allocate pps to conditions so there may be confounding variables
• A population is a group of people who are the focus of the researchers interest, from which a smaller sample is drawn
• A sample is a group of people who take part in a research study. It is drawn from a target population and is presumed to be representative of that population
• random sample -This method gives every member of the target group an equal chance of being selected for the sample
• random sample -

  strength

  • Potentially unbiased, increasing internal validity

  weaknesses

  • Time consuming to conduct
  • You may still end up with an unrepresentative sample or a bias sample
• A systematic method is chosen for selecting from a target group,
• systematic sample -

  strengths

  • Sampling method is objective and the researcher has little influence, reducing bias

  weaknesses

  • Time consuming
  • May not end up with a representative sample e.g. if every 4th pp was male
• A stratified method is where the composition of the sample reflects the proportions of people in certain subgroups in the population
• stratified sample -

  strengths

  • Produced a representative sample and means we can generalise the results to the population

  weaknesses

  • Time consuming
  • Subgroups can not reflect all the ways people are different so complete representation of the population is not possible.
• A opportunity sample uses pps who are both accessible and willing to take part
• opportunity sample -

  strengths

  • This is an easy and inexpensive method

  weaknesses

  • The sample may not be representative and could be subject to bias (the group all share similarities)
• A volunteer sample uses pps who have volunteered to be in the study
• volunteer sample -

  strengths

  • Achieves large samples and can reach a large audience e.g. if done online

  weaknesses

  • Those who volunteer may all show similar characteristics e.g. be interested in psychological research, and therefore may be bias/unrepresentative.