to snoo-finity ... and beyond!
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Contributor score: 4
100/120 = 83% roughly 80%
Not sure what lfsuarez and seagull above mean. Here is my explanation.
Specificity = TN/(TN+FP). This test gave 20 false positives out of 100 people, and only 15 true negatives out of 50 men.
Specificity also equals 1-FPrate, and here the FP rate seems 20% so 100%-20%=80%.
abnormal test result means pt has cancer =>
TP = 35, FN = 15 (50-35), FP=20, TN =80 (100-20) => specificity = TN/(TN+FP) = 80/100 = 0.8 (in % will be 80%)
true negatives are 80 out of 100, not 15 out of 50
If you replace the values from the question in the table of page 257 of FA 2019, yb_26 explanation is correct. Abnormal test = patient has cancer = test +
Question says 35/50 men with prostate cancer (so all 50 have cancer) only 35 have abnormal test results, meaning that TP=35 (disease + test +) and FN= 15 (disease + test - because they do have cancer but the test was not abnormal for them ).
20/100 men without prostate cancer have abnormal test results meaning all 100 DONT have cancer but 20 show that they have cancer when its not true so FP=20 (disease - test +) and TN =80 (disease - test -)
Who said not to use it in old people? Remember "I pray that tio can breathe soon" and tio is an old uncle in spanish but its also the other drug, tiotrropium.