A new screening blood test for a cancer has a sensitivity of 90% and a specificity of 95%. It is proposed for use in the general population aged 50–74, in whom the prevalence of the cancer is 1%. A 58-year-old woman with no symptoms has a positive result and asks what this means.
Of every 100 people in this population who test positive, approximately how many actually have the cancer?
Keep going — a set of ten like this one, one at a time.
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