E. 80% (41/51) – Explanation
Sensitivity and specificity calculations are very commonly asked. Below you would find
a table and a formula to memorise and understand for the purpose of the exam.
| Disease present | Disease absent | |
| Test positive | a | b |
| Test negative | c | d |
Sensitivity = a/(a+c)
Sensitivity measuresthe proportion of actual positives that are correctly identified as
such.
SPECIFICITY AND SENSITIVITY CALCULATIONS
| Disease present | Disease absent | |
| Test positive | a | b |
| Test negative | c | d |
Sensitivity = a/(a+c)
Specificity = d/(b+d)
Positive predictive value = a/(a+b)
Negative predictive value = d/(c+d)
Accuracy = a+d/(a+b+c+d)
