Effective Sample Size and Power Holding m Constant
| Number of Physicians | Number of Patients | Total Number | ρ= 0.017 | Power | |
|---|---|---|---|---|---|
| k | m | (mk) | DE | ESS | tTest* |
| *Power to detect a minimum effect size of 0.5 when one half the clusters is randomly assigned to treatment and the other half to placebo, and mean responses are compared using a 2-sample t test made at the .05 level of significance. | |||||
| m = number of subjects in a cluster; k= number of clusters; mk = total number of subjects in a clustered study; DE = design effect; and ESS = effective sample size. | |||||
| 2 | 10 | 20 | 1.153 | 18 | 16 |
| 4 | 10 | 40 | 1.153 | 36 | 30 |
| 8 | 10 | 80 | 1.153 | 70 | 50 |
| 16 | 10 | 160 | 1.153 | 138 | 83 |