Sample size of 12 per group rule of thumb for a pilot study

By S. Julious. 2005

2,828 citations recorded by the source corpus.

Subfields: Economics and Econometrics, Statistics and Probability

View Paper: https://www.semanticscholar.org/paper/a8a0c7f3b092a0e51009c755bc19187519e0129d

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Economics and Econometrics

In Statistics and Probability

Citations in the corpus

The size of a pilot study for a clinical trial should be calculated in relation to considerations of precision and efficiency. (2012, result): “With specific reference to estimates of the SD, Julious [4] proposes at least n5 12 per group, equivalent to n5 24 for a traditional two-group study, a figure similar to that proposed by other authors [5,6].”
An audit of sample sizes for pilot and feasibility trials being undertaken in the United Kingdom registered in the United Kingdom Clinical Research Network database (2013, background): “Julious [9] recommends a minimum sample size of 12 per group as a rule of thumb and justifies this based on rationale about feasibility and precision about the mean and variance;”
Estimating the sample size for a pilot randomised trial to minimise the overall trial sample size for the external pilot and main trial for a continuous outcome variable (2015, methodology): “Initially a flat rule of thumb was used, and the pilot sample size was chosen to be 24 evaluable patients in total as recommended by Julious.(16) However, suppose that a priori the standardised effect size for the main trial is 0.”
Initial Scale Development: Sample Size for Pilot Studies (2010, methodology): “The primary approach we used was a cost–benefit analysis, similar to Julious (2005), where we identified that point at which a sample size increment produced a notably lesser effect in estimating relevant population parameters.”
Sample size requirements to estimate key design parameters from external pilot randomised controlled trials: a simulation study (2014, background): “A frequently reported problem with publicly funded RCTs is that the recruitment of participants is often slower or more difficult than expected, with many trials failing to reach their planned sample size within the originally envisaged trial timescale and trial-funding envelope.”