Table 3

Pilot trial objectives and methods

CharacteristicNumber of trials (%)
Primary objective is feasibility*10 (56)
Main feasibility objective given
 Where feasibility is primary objective
  Implementing intervention6/10 (60)
  Recruitment and retention3/10 (30)
  Feasibility of cluster design1/10 (10)
 Where feasibility is not primary objective†
  Implementing intervention3/8 (38)
  Recruitment2/8 (25)
  Cluster design1/8 (13)
  Feasibility of trial being able to answer the effectiveness question (and what study design would enable this)1/8 (13)
  Feasibility of larger study1/8 (13)
Method used to address main feasibility objective given
Where feasibility is primary objective
  Descriptive statistics and/or qualitative9/10 (90)
  Statistical test1/10 (10)
 Where feasibility is not primary objective
  Descriptive statistics/qualitative3/8 (38)
  None given/reported elsewhere5/8 (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/efficacy9/18 (50)
Making any statements about effectiveness/efficacy without a caveat4/18 (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.