Chapter 2

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  1. Observational studies
    • Different than controlled experiment
    • do not assign subjects to treatment or control groups. Some subjects have condition whose effects are being studied: this is the treatment group. the other subjects are the controls
    • Smokers= treatment Group) (Non-smokers = Controlled)
    • try to find-out how subject came into groups
    • are the groups comparable? different?
    • what factors are confounded with treatment
    • what adjustments were made for confounding? were the sensible?
  2. Association
    • Observational studies can establish association (one thing is linked to another)
    • association may point out causation (if one group is exposed to chemicals they should be sicker than the other)
    • association does not prove cause: (confounding)
  3. Counfounding
    • Observational studies can be misleading about cause and effect because of confounding
    • Confounding is a third variable associated with exposure and disease.
    • In observational studies a confounding factor can sometimes be ¬†for by comparing other groups which are relatively homogeneous with respect to the factor.
  4. Control Groups Vs Observational
    Questions to ask
    • Ask questions
    • Were there any control groups at all?
    • if so were historical control are contempary used?
    • how were the assigned to groups under the control of an investigator (controlled experiment) or out the control of an investigator (observational experiment)?
    • If controlled were they assigned via (randomized controlled) or at the discretion of the investigator?
  5. Weakness of Observational Studies
    The great weakness is confounding: randomized experiments minimized this problem
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Chapter 2
2015-08-14 05:34:08
Observational studies
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