What does it mean to make the sample size a random variable?

Frank Harrell has started a blog (Statistical Thinking). In his premier post, he lists some key features of his statistical philosophy. Among other items, it includes:

  • Make the sample size a random variable when possible
  1. What does it mean to “make the sample size a random variable”?
  2. What are the advantages of doing this? Why might it be preferable?


I’m not meaning to use models close to the data collecting process but rather doing continuous Bayesian monitoring of posterior probabilities, which require no penalty for multiplicity. Instead of computing an arbitrary target sample size I’d prefer to compute a maximum possible sample size (for budget approval) and otherwise to stop “when we get the answer” as usually done to good effect in physics. I’ll say more about that in my blog http://fharrell.com some day before long.

Source : Link , Question Author : gung – Reinstate Monica , Answer Author : Frank Harrell

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