HY: Biostats

Attributable Risk (AR) Formular

AR = (a/a+b) - (c/c+d)

Attributable Risk Percentage (ARP) Formula

ARP = (RR-1)/RR

Absolute Risk Reduction (ARR) Formula

ARR = (c/c+d) - (a/a+b)

How does NPV change with disease prevalence?

Decreases with increasing disease prevalence

How does PPV change with disease prevalence?

Increases with increasing disease prevalence

Number Needed to Harm (NNH) Formula

NNH = 1/AR

Number Needed to Treat (NNT) Formula

NNT = 1/ARR

Odd Ratio (OR) Formula

OR = (a/b)/(c/d) = ad/bc

Relative Risk (RR) Formula

RR = (a/a+b)/(c/c+d)

Relative Risk Reduction (RRR) Formula

RRR = 1 - RR

NPV Formula

TN/(TN+FN)

Specificity Formula

TN/(TN+FP)

Sensitivity Formula

TP/(TP+FN)

PPV Formula

TP/(TP+FP)

Relationship between Mean/Median/Mode with a Negative Skew

Tail to the left Mean < median < mode

Relationship between Mean/Median/Mode with a Positive Skew

Tail to the right Mean > median > mode