Statistical power
In Trial design & structure
Also known as: sample size
Statistical power is the probability that a trial will detect a real effect of a given size if one exists. Trials are commonly designed for 80% or 90% power, which drives how many participants are needed. An underpowered trial can miss a genuine benefit and leave the question unanswered.
Example
A team calculates that detecting a 10% difference in response rates with 90% power needs roughly 500 participants per arm \u2014 which is what drives the trial's size and budget.
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