Frequently asked questions
How should I enter data in MedCalc to perform ROC curve analysis?
In order to perform ROC curve analysis in MedCalc you should have a measurement of interest (= the variable you want to study) and an independent diagnosis which classifies your study subjects into two distinct groups: a diseased and non-diseased group. The latter diagnosis should be independent from the measurement of interest.
In the spreadsheet, create a column DIAGNOSIS and a column for the variable of interest, e.g. TEST1. For every study subject enter a code for the diagnosis as follows: 1 for the diseased cases, and 0 for the non-diseased or normal cases. In the TEST1 column, enter the measurement of interest (this can be measurements, grades, etc. - if the data are categorical, code them with numerical values).
In the dialog panel for ROC curves enter the following:
Classification variable: DIAGNOSIS
Click OK to see the results.
If diagnosis is coded differently than using the values 0 and 1, but for example using the text codes "pos" and "neg", you can use the IF function to transform the codes into 0 and 1 values, and enter e.g. IF(DIAGNOSIS="pos",1,0) for Classification variable.
See also: ROC curve analysis section of the MedCalc manual.