 # Sensitivity Specificity Equations

4528 Views 4 Replies 5 Participants Last post by  rasheed
Sensitivity is also called the True Positive Rate
Specificity is also called the True Negative Rate
Sensitivity = TP rate
Specificity = TN rate

1 = TP rate + FN rate
therefore 1 - Sensitivity = FN rate
or Sensitivity = 1 - FN rate

1 = TN rate + FP rate
therefore 1 - Specificity = FP rate
or Specificity = 1 - FP rate

Increasing Prevalence increases positive predictive value and deceases the negative predictive value but it has nothing to do with sensitivity or specificity.

The Receiver operating Curve plots sensitivity(TP rate) in the Y axis and 1-Specificity (FP rate) in the X axis, area under the curve will be the accuracy of the test.
• 1
1 - 5 of 5 Posts
Are these high yield?

I think understanding the 2X2 box is all that's needed for both USMLE Step 1 and USMLE Step 2 CK
what is the box

I have not done epidemiology yet and would like an explanation of what the box is
The box is "Disease / No Disease" vs "Positive / Negative".

Basically, Disease + Positive = True Positive (usually the upper left box), whereas No Disease + Negative = True Negative (usually lower right box).

The box is high-yield. • 1
• 1
1 - 5 of 5 Posts