calculateCutoffs        Calculate data filtering results and two
                        cutoffs for given sensitivity and specificity
                        threshold
createData              Generate simulation data
discretizeAge           Discretize the age variable according to the
                        two cut-off points
findCutoffs             Finding the two cut-off points
fitLogisticRegression   Fit a logistic regression model and return the
                        OR and 95% confidence interval
fitSemiParamModel       Fit the data using a semi-parametric model to
                        explore the nonlinear dose-response
                        relationship between the independent variable
                        and lnOR
