Question

Frequency of Flu cases Frequency of Non-flu Cases Frequency of individual who screened positive 94 20 Frequency of individuals who screened negative 86 200 Assume the above results were obtained in a study used to test the accuracy of the rapid diagnostic test for influenza. Calculate and interpret the specificity of the rapid diagnostic influenza test.

Answer 1

Solution: Let us tabulate the given data from the question.

	Frequency of flu cases	Frequency of non-flu cases
Frequency of individual who screened positive	94(TP)	20(FP)
Frequency of individual who screened negative	86(FN)	200(TN)

Where TP= True positive, FP=False positive, FN=False negative and TN= True negative

Formula to calculate specificity is as follows:

Specificity= Number of true negatives/(Number of true negatives+ Number of false positives)

Let us use the numbers from the above table to calculate the specificity.

So, Specificity=200/(200+20)=0.9090=90.9%

We can say that 90.9% specific that the individuals do not have flu.