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Relative Risk (RR)
- RR = a / (a+b)
- c / (c+d)
- RR = 1: no difference between groups
- RR < 1:less likely to occur in treatment group
- RR > 1:more likely to occur in treatment group
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Relative Risk Reduction (RRR)
RRR = 1 - RR
OR
- RRR = (% risk in control - % risk in treatment) % risk in control
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Absolute Risk Reduction (ARR)
ARR = % risk in control - % risk in treatment
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Number Needed to Treat (NNT)
NNT = 1 / ARR
OR
NNT = 1 / (% risk in control - % risk in treatment)
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Odds Ratio (OR)
OR = ad / bc
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Hazard Ratio (HR)
HR = hazard treatment arm / hazard control arm
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nominal data
- consists of categories: ex; gender, ethnicity
- * numbers have no true numerical value, ex; male - 1, female - 2
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ordinal data
ranked categories: like NYHA scale, or pain scale
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continuous data
- infinite number of possible values, ex; height, weight, A1C, blood pressure
- interval data: difference between 2 values, ex; celsius temp
- ratio data: height, weight, time, length
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