Statistics - explanations and formulas

Control Event Rate

Control Event Rate is the proportion of patients in the control group who experience the studied event.

In order to calculate it, you will also need to understand Relative Risk Reduction and Absolute Risk Reduction, explained elsewhere in this guide.

Control Event Rate (CER) = c/c+d. Relative Risk Reduction (RRR) = CER-EER/CER. Absolute Risk Reduction (ARR) = CER-EER. Absolute Risk Increase (EER-CER

This example is from: Lipman, G. S., Pomeranz, D., Burns, P., Phillips, C., Cheffers, M., Evans, K., Jurkiewicz, C., Juul, N., & Hackett, P. (2018). Budesonide versus acetazolamide for prevention of acute mountain sickness. The American Journal of Medicine, 131(2), 200.e9–200.e16

Outcome (Yes)

Outcome (No)

Experimental Group Acetazolamide N=35

15

20

35

Control Group Budesonide N=33

24

9

33

39

29

68

Control Event Rate is the proportion of patients in the control group who experience the studied event.

24/24+9=.73 (rounding up)

To learn more about using tables in Control Event Rate, visit this webpage.