Table 3.
Pilot trial objectives and methods
| Characteristic | Number of trials (%) |
| Primary objective is feasibility* | 10 (56) |
| Main feasibility objective given | |
| Where feasibility is primary objective | |
| Implementing intervention | 6/10 (60) |
| Recruitment and retention | 3/10 (30) |
| Feasibility of cluster design | 1/10 (10) |
| Where feasibility is not primary objective† | |
| Implementing intervention | 3/8 (38) |
| Recruitment | 2/8 (25) |
| Cluster design | 1/8 (13) |
| Feasibility of trial being able to answer the effectiveness question (and what study design would enable this) | 1/8 (13) |
| Feasibility of larger study | 1/8 (13) |
| Method used to address main feasibility objective given | |
| Where feasibility is primary objective | |
| Descriptive statistics and/or qualitative | 9/10 (90) |
| Statistical test | 1/10 (10) |
| Where feasibility is not primary objective | |
| Descriptive statistics/qualitative | 3/8 (38) |
| None given/reported elsewhere | 5/8 (63) |
| Rationale for numbers in pilot trial based on formal power calculation for effectiveness/efficacy‡ | 0/8 (0) |
| Performing any formal hypothesis testing for effectiveness/efficacy | 9/18 (50) |
| Making any statements about effectiveness/efficacy without a caveat | 4/18 (22) |
*Where the primary objective was not feasibility, the primary objective was effectiveness/potential effectiveness and was addressed using statistical tests.
†One of the inclusion criteria was that studies were assessing feasibility, but it did not have to be the primary objective.
‡Based on eight trials that reported a rationale for the sample size of the pilot trial.