Meseasures Of Assocation Flashcards
(13 cards)
In which type of epidemiological study is the Odds Ratio (OR) typically used?
Case-control studies.
How is the Odds Ratio (OR) calculated using a standard 2x2 table (A=exposed cases, B=exposed controls, C=unexposed cases, D=unexposed controls)?
OR=BC/AD (Odds of exposure in cases / Odds of exposure in controls).
How do you interpret an Odds Ratio (OR) value greater than 1? Less than 1? Equal to 1?
OR>1: Risk factor (increased odds). OR<1: Protective factor (decreased odds). OR=1: No association.
In which type of epidemiological study is the Relative Risk (RR) typically used?
Cohort studies.
How is the Relative Risk (RR) calculated?
RR=Incidence_unexposed/Incidence_exposed = c/(c+d) / a/(a+b) (Incidence in exposed / Incidence in unexposed).
How do you interpret a Relative Risk (RR) value greater than 1? Less than 1? Equal to 1?
RR>1: Increased risk in exposed. RR<1: Decreased risk in exposed (protective). RR=1: No difference in risk.
How is the statistical significance of an Odds Ratio (OR) or Relative Risk (RR) typically assessed using a confidence interval?
A 95% Confidence Interval (CI) that does not cross 1.0 indicates a statistically significant association.
What does Attributable Risk (AR) measure, and how is it calculated?
Measures the excess risk attributable to the exposure. Formula: AR=Risk_exposed−Risk_unexposed.
How is Vaccine Efficacy calculated?
Vaccine Efficacy=Risk_unvaccinated(Risk_unvaccinated−Risk_vaccinated)×100. This can also be expressed as (1−RR)×100.
What is the key difference between association and causation in epidemiology?
Association is an observed link between exposure and outcome. Causation implies the exposure causes the outcome and requires fulfilling additional criteria (like the Bradford Hill criteria).
Efficacy:
Effectiveness:
• Efficacy: Measured under ideal trial conditions.
Effectiveness: Measured under real-world field conditions,
Attributable Proportion:
• Calculates: The proportion of risk in the exposed group that is attributable to the exposure. Formula: AttributableProportion= AR /Risk exposed ×100
Association vs. Causation:
Association: An observed link between exposure and outcome.
Causation: Implies that the exposure causes the outcome. Establishing causation requires more than just a statistically significant association.
Criteria for Causation (Bradford Hill Criteria - summarized): Strength, Consistency, Specificity, Temporality (exposure precedes outcome), Biological Gradient (dose- -response), Plausibility, Coherence, Experiment, Analogy.
