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The number needed to screen is an estimate of how many people need to be screened before one person would experience a good outcome.
For example, if a study found that for every 1000 participants allocated to screening for cancer there was one less death from that cancer over a period of ten years compared to every 1000 people allocated to not receive the screening test, the number needed to screen would be 1000, for ten years.
number needed to treat · screening
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