Sampling

• What are the five sampling techniques?

  Random, systematic, stratified, opportunity, volunteer
• What is a population?

  A group of people who are the focus of the researcher
• Population: A group of people who are the focus of the researcher
• Sample: A group of people drawn from the population who take part in the investigation
• What is bias?


  Where certain groups are over/under represented within a sample
• What is the effect of bias?

  Limits generalisability from the sample to the population
• What is generalisation?

  The extent to which findings can be applied to the population
• The sample drawn from the population must be representative so generalisation is possible
• What is a sample?

  A group of people who take part in an investigation drawn from a population
• What is random sampling?

  All members of a target population have an equal chance to be selected
• How do you complete a random sample?

  1 ) Obtain list of population

  2 ) Assign names w/ numbers

  3 ) Sample selected thru lottery methods
• What is a systematic sample?

  Where every nth member of the target population is selected
• How do you complete a systematic sample?

  1 ) Produce sampling frame

  2) Nominate sampling system

  3 ) Work through until sample is complete
• What are strata?

  Sub-groups
• What is a stratified sample?

  The composition of the sample reflects the proportions of people in certain strata within the population
• How do you complete a stratified sample?

  1 ) Identify strata

  2 ) Proportions worked out

  3 ) Participants making up each strata selected by random sampling
• What is an opportunity sample?

  Selecting anyone who is willing and available
• What is a volunteer sample?

  Participants selecting themselves (self-selection)
• How do you complete a volunteer sample?

  Placing an advert in a newspaper
• Strengths: Random sampling

  Unbiased - internal validity
• Limitations: Random sampling

  Time-consuming

  Can be unrepresentative

  May refuse to take part
• Strengths: Systematic sampling

  Objective
• Limitations: Systematic sampling


  Time-consuming

  May refuse to take part
• Strengths: Stratified sampling

  Representative

  Generalisable
• Limitations: Stratified sampling

  Stratification is not perfect - not completely representative
• Strengths: Opportunity sampling

  Convenient - less costly/time-consuming
• Limitations: Opportunity sampling

  Bias - researcher bias/unrepresentative
• Strengths: Volunteer sampling

  Easy - less costly/time-consuming

  More engaged participants
• Limitations: Volunteer sampling

  Volunteer bias