Sampling

• What is a sample?


  A group of people who take part in a research investigation
• What is bias in terms of sampling?


  When certain groups are under or over represented within the sample selected
• What is a Random Sample?


  Everyone has an equal opportunity of being picked

  Use a random number generator
• Strengths of Random Sampling

  1. Unbiased
  2. Representative
• Weakness of Random Sampling

  1. Impractical as it is hard to include everyone in the population
  2. Time consuming
• What is Systematic Sampling?

  Selecting PPs from a target population by selecting them at pre set intervals

  e.g selecting every 50th person in a list
• Strengths of Systematic Sampling

  1. Unbiased so no researcher bias
  2. Representative
• Weakness of a Systematic Sampling

  Unexpected bias so certain types of people may only be chosen so some never get picked
• What is Stratified Sampling?

  Dividing the population into relevant groups work out the % of groups

  When splitting groups you get a % of that group to make the sample
• Strengths of Stratified Sampling

  1. Representative
  2. Unbiased
• Weakness of Stratified Sampling

  Need knowledge of the population breakdown

  Not doing the groups right leads to bias
• What is Volunteer Sampling?


  PPs offer to take part in the sample

  Placing on advert online telling people to ask questionnaire
• Strengths of Volunteer Sampling

  1. Quick and easy
  2. No experimenter bias
• Weaknesses of Volunteer Sampling

  1. Unrepresentative as certain types of people may volunteer
  2. Time consuming
• What is Opportunity Sampling?


  Approaching people who are available and asking them to take part in the sample

  Asking people on the street to do a questionnaire
• Strengths of Opportunity Sampling

  1. Quick and easy
  2. May be the only option
• Weakness of Opportunity Sampling

  1. Unrepresentative
  2. Experimenter Bias