Interactive dot diagram

Command:

Statistics ROC curves Interactive dot diagram

Description

In addition to the ROC curve, MedCalc offers a second graphical display to study the accuracy of a diagnostic test, namely an Interactive dot diagram.

Required input

Variable: identify the variable of interest.

Classification variable: select or enter a dichotomous variable indicating diagnosis (0=negative, 1=positive). If diagnosis is coded differently than using the values 0 and 1, you can use the IF function to transform the codes into 0 and 1 values, e.g. IF(RESULT="pos",1,0).

Select: (optionally) a selection criterion in order to include only a selected subgroup of cases (e.g. AGE>21, SEX="Male").

Options: Log transformation of data.

Graph

In the graph the data of the negative and positive groups are displayed as dots on two vertical axes. Initially, a horizontal line indicates the cut-off point with the best separation (minimal false negative and false positive results) between the two groups. The corresponding test characteristics sensitivity and specificity are shown at the right side of the screen display.

By clicking in the display, you can move the horizontal line to other values or cut-off points.