I have three groups with ~ 15 individuals per group.
Group 1 gets a treatment
Group 2 is a control in the same area
Group 3 is a further control in a different area
The response is binary, 1 or 0.
I want to determine the power of my study. I used this calculator but would like a second opinion. Using the terms from that site:
- 2 independent study groups
- A dichotomous endpoint
- alpha = 0.05
- power = 80%
- 50% expected incidence in group 1
- 10% expected incidence in group 2
- an enrollment ratio of 2:1 because I lump my controls together (groups 2 and 3)
This gives a sample size of 14 for group 1 and 28 for group 2.