Power — What It Means in Clinical Trials
Plain English Definition
Statistical power is the probability that a trial will detect a treatment effect if one truly exists. Most trials aim for 80% or 90% power, meaning they have an 80-90% chance of finding a real difference between treatments. Higher power requires more participants but produces more reliable results.
Why It Matters
A trial with low power might miss a real treatment benefit. If a trial reports "negative" results (no difference found), check its power — an underpowered trial may simply not have had enough participants to detect the effect.
Example
A trial protocol might state: "The study is powered at 80% to detect a 20% improvement in progression-free survival." This means there is an 80% chance of finding this improvement if it truly exists.
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