3 ms·
Dumb question: does "90% accuracy" mean - "of the cancers it detected, it was 90% correct"? Or does it mean, "of all the patients who developed cancer, it dete
by tiffanyh 2y ago
Dumb question: does "90% accuracy" mean - "of the cancers it detected, it was 90% correct"?
Or does it mean, "of all the patients who developed cancer, it detected 90% of them"?
Where the later is referring to the entire population, and the former is only about those detected.
- vostok 2y agoI really like the table of confusion as a way to look at this stuff. I find the terminology somewhat confusing and it's much easier for me to just look up the formulas. That means 90% accuracy should mean (true_positive + true_negative)/(whole_population) == 90%. https://en.wikipedia.org/wiki/Confusion_matrix https://en.wikipedia.org/wiki/Confusion_matrix
- diffeomorphism 2y agoSo a trivial test that always says "No" will have better accuracy? https://www.cancer.org/cancer/types/prostate-cancer/about/key-statistics.html https://www.cancer.org/cancer/types/prostate-cancer/about/ke... > About 1 in 8 men will get diagnosed with that cancer, through their whole lifetime. So true_negative/whole_population>=87.5% at least (life time vs currently has cancer). Or am I misunderstanding the meaning?
- greenavocado 2y agoThis is why accuracy is useless for reasoning about detection of rare things.
- _Microft 2y agoBeside the already linked-to article on the confusion matrix, you can also have a look at the one on sensitivity and specificity: https://en.m.wikipedia.org/wiki/Sensitivity_and_specificity https://en.m.wikipedia.org/wiki/Sensitivity_and_specificity