Skip to main content
Mail a PDF copy of this page to:
(Your email address will not be added to a mailing list)
Show menu

Comparison of two rates

Next selectRates
Next selectComparison of two rates


An incidence rate is a ratio between a count and another measurement, for example the ratio of a number of events observed and the total number of person-years of observation.

This procedure allows to compare the incidence rates in two groups.

This test is not performed on data in the spreadsheet, but on data you enter in a dialog box.

Required input

Comparison of rates

When all data have been entered click Test.


MedCalc reports:

For the confidence interval of the difference between two rates, MedCalc uses the "Test based Method" given on page 169 of Sahai H, Khurshid A (1996). The P-value is obtained using the Chi2-statistic.

For the confidence interval of the incidence rate ratio, MedCalc uses the "Exact Poisson Method" given on page 172-174 of Sahai H, Khurshid A (1996). The P-value is the exact mid-P double sided P-value (Hanley, 1986)

In the Comment input field you can enter a comment or conclusion that will be included on the printed report.


See also