Evidence-Based Practice / Unit 22 EBP 3189 short lesson, about 20 seconds
Misconception: A Bigger Sample Fixes a Biased One
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The idea
Increasing the size of a biased sample produces a more precise estimate of the wrong number. Size addresses precision, and only selection addresses bias.
In practice
Ten thousand volunteers, all of whom chose to participate for the same reason.
Where people slip
This is the sampling counterpart to unit 22's attrition point: what is wrong with the sample is not repaired by having more of it.
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