sampling

• Stratified sampling?

  • Divide target population into subcategories
  • Select members in the proportion they occur in the population
  • When the quote for a category is filled the researcher moves onto the next one
• Random sampling?

  • Every member of a population has an equal chance of being selected
  • eg. pulling names out of a hat
• Systematic sampling?

  • Choose your participants from a sampling frame using a system
  • eg numbering the participants 1,2,3 and then selecting every 3rd person to be a participant every 3rd person to be a participant
• Opportunity sampling?

  • Simply selecting those people that are available at the time
  • eg. going up to people in cafes and asking them to be interviewed
• Quota sampling?

  • Dividing the target population into important subcategories
  • Selecting members in proportion that they occur in the population
  • 2.5% of British are of Indian origin, so 2.5% of the sample should be etc
• Volunteer sampling?

  • Individuals who have chosen to be involved in a study
• Snowball sampling?

  Participants are selected from an initial contact who puts the researcher in touch with other possible participants
• Advantage of snowball sampling?

  A useful way of finding participants with a certain attribute (eg cult member) who might not wish to be found otherwise
• Disadvantage of snowball sampling?

  • Can be very biased, people with more friends are more likely to be selected as participants
  • Some people might not want to be 'found' by sociologists
• Advantage of volunteer sampling?

  • Relatively convenient and ethical if it leads to informed consent
• Disadvantage of volunteer sampling?

  Unrepresentative as it leads to bias on the part of the participant eg a daytime TV advert would not attract full time workers
• Advantage of quota sampling?

  A deliberate effort is made to make it representative
• Disadvantage of quota sampling?

  It can be time consuming as the subcategories have to be identified and proportions calculated
• Advantage of opportunity sampling?

  • Quick, convenient and economical
  • A most common type of sampling in practice
• Disadvantage of opportunity sampling?

  • Very unrepresentative samples and often biased by the researcher who will likely choose people who are 'helpful'
• Advantage of systematic sampling?

  • Can give unbiased samples from large populations
• Disadvantage of systematic sampling?

  In some situation using a system to select participants can make the sample biased eg by picking every 10th house you may only pick corner houses etc
• Advantage of random sampling?

  For very large samples it provides the best chance of an unbiased representative sample
• Disadvantage of random sampling?

  For large populations it is time-consuming to create a list of every individual
• Advantage of stratified sampling?

  A deliberate effort is made to make the sample representative of the target population
• Disadvantage of stratified sampling?

  It can be time consuming as the subcategories have to be identified and proportions calculated
• Types of sampling?

  • Snowball
  • Volunteer
  • Quota
  • Opportunity
  • Systematic
  • Random
  • Stratified