Definition

The Log-rank test is used to compare survival or time before an event occurence between two or more groups. It compares the observed number of events and compares it to the expected number of events, per group, at each time. Doing this, the Log-rank test compares hazard functions of the two groups which is the instantaneous failure rate.

You should do a Log-rank test if you want to compare the difference in survival or time before an event occurence between groups and make conclusions about the extrapolation of the results observed in the study sample to a target population.

How to use it on EasyMedStat?

1. Create an Event variable
2. Go to Statistics > Descriptive
3. Go to the Event variable you want to analyze and click on "Kaplan-Meier"
4. Go to the panel "Compare survivals" and choose the variable you want to compare your groups by.
   For example, if you want to compare the survival of Men and Women, choose the variable "Gender" in the List

You can only compare survival by a discrete variable, ie, a List or Yes-no variable. It is not possible to use a Numeric variable or an Event variable to compare two survivals.

See also

• The Kaplan-Meier estimator
• The survival median
• The complementary log-log transformation