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Epidemiology Y1S2 (Class Assignment (1) Adv of cross-sectional, 2)…

- - - - Cumulative Incidence / Incidence Proportion + Rate/Risk:
        Definition: Probability of occurrence per unit time
        Numerator: Total number of subjects who developed outcome of interest
        Denominator: Total number of subjects "at risk" being followed
        Requires: A specific time period to be stated. Just an "if" factor not "when.
        Note: The rate/risk words are often omitted even though it involves a specific time factor
      - Incidence Rate/Risk:
        Definition: Probability of occurrence per unit time
        Numerator: Total number of subjects who developed outcome of interest
        Denominator: Total amount of time (person-hours) subjects followed spent "at risk"
        Requires: Consistent periodic follow up, not just if outcomes develops, but when
- - - - Cohort Study (Selecting subjects by variable first)
        
        Prospective / Retrospective
        
        Historical Prospective
        
        Advantages and Disadvantages (Slide 31)
        
        Relative Risk: % occurrence of disease in exposed / Raw occurrence of disease in unexposed group.
        Probability of developing outcome as an exposed is __ times more/less than unexposed
      - Case Control Study (Selecting subjects by disease first)
        
        Retrospective
        
        Try to select case and control groups which are as similar as possible
        
        Advantages and Disadvantages (Slide 25)
        
        Odds ratio: Cross product: Product of correct outcome / Product of incorrect outcomes. If you had desired outcome, you are ___ times more likely to be exposed than unexposed
      - Ecologic Studies
    - - Randomized Control Trial / Clinical Trial
        
        1) Select sample population of interest
        
        2) Split into treatment and control group (as similar as possible - prevent confounding)
        
        3) Give one group intervention
        
        4) Control tightly
      - Community Intervention
      - Challenges
        
        External Validity: Ability to generalize your findings to general population
        
        Bias: Systematic deviation of results fro truth
        
        Confounding
        
        Association and Causation
      - Sensitivity & Specificity (Based on Odds Ratio)
        True positive x True negative divided by
        False positive x False negative
        
        True positive
        
        False Negative
        
        True Negative
        
        False Positive
        
        Definition of Sensitivity:
        
        Definition of Specificity:
  - - - Cross-sectional: Snapshot of situation at particular point in time (Examine relationship between diseases and other variables)
      - Longitudinal Studies: Video
    - - Case Series (Series of patients with similar but unusual symptoms or outcomes)