Table 1 Observations and parameters by group and actual treatment for the 2-stage randomised design
Actual treatment |  | Choice arm (Total sample size = m) | Random arm (Total sample size = n) | ||
|---|---|---|---|---|---|
| Â | Â | Choose A | Choose B | Undecided (and randomised) | |
A | Sample size | m 1 | — | m 3 /2 | n 1 |
Observations | x 11 ,…x 1,m1 |  | v 11 ,…v 1,m3/2 | y 11 ,… y 1,n1 | |
Mean | μ 11 | (μ 12 ) | μ 13 | μ 1 | |
SD | σ 11 |  | σ 13 | σ 1 | |
B | Sample size | — | m 2 | m 3 /2 | n 2 |
Observation |  | x 21 ,…x 2,m2 | v 21 ,…v 2,m3/2 | y 21 ,…y 2,n2 | |
Mean | (μ 21 ) | μ 22 | μ 23 | μ 2 | |
SD |  | σ 22 | σ 23 | σ 2 | |