Sample selection and size

All pilot and feasibility studies submitted to the HiREB, from January 2004 to December 2020, inclusive, that used the terms “pilot” or “feasibility” in their title and obtained participant consent were included in our study. All pilot and feasibility studies that had a waiver of consent were excluded.

To determine the sample size, we used the estimation method for a single proportion [17, 19]. The statistical formula behind the method uses an estimation for a single proportion—the proportion can be from a variable tested in the study and calculates the sample size needed for a given margin of error of the estimate and confidence interval (CI). In this method, an estimated proportion of 50% yields the largest necessary sample size. Thus, if the true proportion of pilot studies that use the term “pilot” or “feasibility” in the title of the study, as stated on the consent form, is 0.5, which will be estimated with a 95% CI and margin of error 0.40 to 0.60, then a sample size of 96 would be sufficient to address our objectives. We decided that if more than 96 studies met the inclusion criteria, we would include all of them in our study up to a maximum of 500, to decrease the width of the CI.