Tag Archives: Pilot studies

PMean: Slapping the word “pilot” on a failed study

Someone was asking on the MedStats listserv about a study that had gone off the rails. They had recruited only about a third of the patients that they had wanted. Things were going pretty well in the first arm of the study, but the second arm had a dropout rate of 50%.

Anyway, they decided to end the study (good call!) and wanted to know what they should do with the data that they had already collected. There were three options that they were considering (I’m paraphrasing a bit here).

  1. Analyze the study as originally planned, including a classic test of hypothesis for the primary outcome.
  2. Call this a pilot study and provide descriptive analyses only.
  3. Recognize that the data is so fatally flawed that any analysis of the data would be inappropriate.

This is what I suggested. Continue reading

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

This study is (sadly) not available for free on the Internet, but it is still worth highlighting here. Steven Julious provides some justification for the use of twelve patients per group in a pilot study. This is a useful starting point for discussion, and it may serve as a useful lower bound. I would suggest that you consider the size of the larger trial that you are piloting. For a larger study that might require thousands or tens of thousands of patients, a pilot study of 12 patients per group is woefully inadequate. Continue reading