Experimental event rate


In epidemiology and biostatistics, the experimental event rate is a measure of how often a particular statistical event occurs within the experimental group of an experiment.
This value is very useful in determining the therapeutic benefit or risk to patients in experimental groups, in comparison to patients in placebo or traditionally treated control groups.
Three statistical terms rely on EER for their calculation: absolute risk reduction, relative risk reduction and number needed to treat.

Control event rate

The control event rate is identical to the experimental event rate except that is measured within the scientific control group of an experiment.

Worked example

In a trial of hypothetical drug "X" where we are measuring event "Z", we have two groups. Our control group is given a placebo, and the experimental group is given drug "X".
Event "Z" in control group : 4 in 25 people
Control event rate : 4/25
Event "Z" in experimental group : 12 in 25 people
Experimental event rate : 12/25
Another worked example is as follows: