Measures of Association & Effect Flashcards
What are measures of association used for?
Used to quantify the relationship between an exposure and an outcome to find a causal relationship, to develop effective interventions - Do this second
What are measures of frequency used for?
To determine how often an outcome occurs to help determine importance and guide planning. - Do this first
What are measures of impact use for, and name them?
To assess impact of exposure on causation - A.F - A.R. - Prev Ratio Do this third (if a casual rel. exists)
Name measures of Association?
IRR
PR
OR
RR - important for PH importance
Considerations of Risk Ratio for determining an issues PH importance?
- RR < 1 = preventative factor (exposed at lower risk than unexposed) e.g. flouride water
- RR = 1 = No difference in risk between groups
- RR> 1 = exposed at higher risk e.g smoking
Note the further away from 1 the ratio is, the stronger the association NB
how do we turn RR into a %?
RR-1 X 100 %
Prevelence Ratio
Prev in exposed group/ prev in unexposed
cross-sectional studies
Risk Ratio
risk of outcome in exposed / risk in unexposed
AKA cumulative incidence risk (ecological or cohort studies)
Odds Ratio
odds in exposed / odds in unexposed
Case control ONLY
2x2 Tables
- used to sort data and present
Exposure Outcome Total
Y Y N
N
IRR
Incidence rate in exposed group / IR in unexposed
Only use when measure of frquency is IR.
Ecological and cohort
What is background risk?
The frequency of an outcome occuring in the unexposed group/individuals
(measures of impact)
Attributable Risk
Freq. in exposed - Freq. in unexposed
Attributable Fraction/%
Freq in exposed - freq in unexposed / freq. in exposed
Pop Attributable Fraction
freq. in exposed - freq in unexposed / freq. in pop
risk in whole pop - risk in unexposed
