Individual variability
Population averages can hide different responses across individuals.
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Population averages can hide different responses across individuals. A biomarker is a measurable signal associated with a state or outcome, not automatically a cause. Patient stratification groups people for a defined purpose; longitudinal data tracks changes within people. Design comparisons around the clinical question and avoid treating repeated visits as independent patients.
Worked example
If average response is zero but half improve and half worsen, inspect distributions and a prespecified marker. A marker correlated with response still needs validation in new patients.