Epidemiologist – studies patterns in the occurrence of diseases

Cohort studies – follows a group of people over time to see who develops the risk and who doesn’t

Case-control studies – people with the disease are compared to people without

  • Controls should be representative of the population from which the case group was drawn from

Features of a good study

  • Clear aim
  • Representative sample – otherwise selected bias occurs
  • Consider people who are asked to do the study with people who respond (e.g. unemployed people may agree to day-time interviews but they may be [physically unhealthier than employed people who are working thus cannot do the interview)
  • Proportion who drop out should be kept to a minimum so that the remaining are still representative of target population
  • Valid + reliable results
  • Control variables or else may influence outcome
  • Repeatability + reproducibility
  • Same method used
  • Large sample