Data and Sampling

• Sampling

  • Target pop can’t be tested
  • Representative: Generalisable (pop validity)
  • Unrepresentative: Over-/under- (sampling bias)

  Random

  • Representative
  • Unbiased
  • No researcher influence so generalisable
  • Hard unless pop small
  • Some won't consent; unrepresentative

  Opportunity

  • Ethical
  • Easy
  • Quick
  • Large sample
  • Unrepresentative
  • Selection bias, ungeneralisable

  Stratified

  • Proportional representation
  • Time-consuming
  • Difficult find correct proportions

  Volunteer

  • Motivated
  • Less likely drop out
  • Easier than random
  • Unrepresentative
  • Ungeneralisable
  • Demand Characteristics