Evaluate Hypotheses - Analytical studies ** Must have a control group **

  1. Compare with established fact - these are used when evidence is strong and clear cut
  2. Must have lab verification to validate a hypothesis
  3. Two types of Studies : (Study determinants of health problems - how and why)
    • Cohort: Based upon exposure status whether or not they have outcome (illness); used with a small well-defined population and moves forward from exposure. Both groups have a known exposure and are checked for future outcomes or illness.
      • retrospective: (historic cohort) starts at exposure in past and moves forward to outcome
      • prospective: starts at current exposure and moves forward in time to outcome
      • calculations: attack rate and relative risk
    • Case-Control: Works backwards from effect or illness to suspected cause. Control group is a selected group who has similar characteristics to the sick group but is not ill. They are then checked for similar exposures. It is often hard to select the control group for this type of study.