Comparison of two rates
Command: |
Tests
 Rates
 Comparison of two rates |
Description
A 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 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
- Numerator: the observed number of events in each group.
- Denominator: for example the total person-years for each group.
- Option Express result as 1:X: when this option is selected the rate R will be displayed as 1:(1/R), e.g. the rate 10/200 equals 0.05 and can be represented as 1:20.
When all data have been entered click the Test button.
Results
The program displays:
- The (incidence) rate in the two groups with their Poisson 95% Confidence Interval.
- The difference between the two rates R2-R1 with its 95% Confidence Interval and associated P-value. If the P-value is less than 0.05 it can be concluded that there is a statistical significant difference between the two rates.
- The ratio of the two rates R1/R2 and its 95% Confidence Interval. If the value 1 is not in this interval, it can be concluded that the ratio R1/R2 is not significantly different from 1 (in which case the rates would be equal).
In the Comment input field you can enter a comment or conclusion that will be included on the printed report.
Literature
- Sahai H, Khurshid A (1996) Statistics in epidemiology: methods, techniques, and applications. Boca Raton, FL: CRC Press, Inc.
See also
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