Statistics that describe data : Percentages ; Mean ; Median ; Mode ; Standard deviation -- Statistics that test confidence : Confidence intervals ; P values -- Statistics that test differences : t tests and other parametric tests ; Mann-Whitney and other nonparametric tests ; Chi-squared test -- Statistics that compare risk : Risk ratio ; Odds ratio ; Risk reduction and numbers needed to treat -- Statistics that analyze relationships : Correlation ; Regression -- Statistics that analyze survival : Survival analysis: life tables and Kaplan-Meier plots ; The Cox regression model -- Statistics that analyze clinical investigations and screening : Sensitivity, specificity, and predictive value ; Level of agreement and Kappa -- Other concepts -- Statistics at Work : Standard deviation, relative risk, and numbers needed to treat ; Odds ratios and confidence intervals ; Correlation and regression ; Survival analysis ; Sensitivity, specificity, and predictive values.