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i have no clue (Proportion (Prevalence (p) (Point prevalence, Period…
i have no clue
Proportion
Prevalence (p)
Point prevalence
Period prevelance
Measure the people (cant exceed 100%)
Prevalence~ Incidence x time
Cumulative Incidence proportion (IP/CI)
Unit of analysis is event (can exceed 100%)
Measures events (can exceed 100%)
Open population--->
Not reliable for open populations
numerator part of the denominator
time is fixed for everyone
Rate
Incidence density rate (IR)
mean time to event= 1/R
Numerator is not part of the denominator
Involves time
Effect magnitude measures
Relative measures
Risk Ratio
Incidence (density) ratio (IRR)
Cumulative incidence ratio (CIR)
Prevalence ratio (PR)
RR for exposed = 1/RR for unexposed
RR for outcome "y" does not equal 1/RR for "not y"
Compares two different groups
Tells how many times higher/lower the risk is for exposed compared to non exposed
Odds Ratio
Odds
Compares in one group
Odds ratio
Value of OR is more extreme than RR
OR is symmetrical so it can be interpreted both ways around
When disease is rare RR~OR
Strength of relationship
assessing causation
Absolute measures
how much can be attributed to certain exposure (burden/impact)
making clinical decisions
Difference between two measures
R1-R2
RD=RRRxcER
NNT
= 1/RD
How many patients do u need to treat to save one life
Decreases with increase in time
Population risk difference
pER-cER
RDxPPE (poplation % exposed)
Absolute measures as proportions
Attributable proportion among exposed (APE)
RD/eER
[(eER-cER)/eER] x 100
[(RR-1)/RR] x 100
[(OR-1)/OR] x 100
Risk in non-exposed can be considered as "background"
