title: A method for determining the size of internal pilot studies.
abstract: The assessment of sample size in clinical trials comparing population means requires a variance estimate of the main efficacy variable. When this variance estimate has a low precision, it may be appropriate to use the data from the first patients entered in the trial ('internal pilot study') to estimate the sample size. We suggest a method for determining the size of internal pilot studies, which aims at ensuring that this size is as large as possible, but not larger than 'the optimal size' of the planned study. Advantages and limitations of the method are discussed.
authors.affiliation: Medstat Research A/S, Lillestrøm, Norway.
authors.forename: L
authors.initials: L
authors.lastname: Sandvik
authors.forename: J
authors.initials: J
authors.lastname: Erikssen
authors.forename: P
authors.initials: P
authors.lastname: Mowinckel
authors.forename: E A
authors.initials: EA
authors.lastname: Rødland
mesh_terms: D015982:Bias; D010865:Pilot Projects; D011336:Probability; D016032:Randomized Controlled Trials as Topic / Q000379:methods; D018401:Sample Size