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