# Is it correct to define the F-measure as the harmonic mean of specificity and sensitivity in such a way?

It is common to define the F-measure as a function of precision and recall, as mentioned in [1]:

$$F_{\beta}=\frac{(1+\beta^2)PR}{\beta^2 P+R}$$

However I came across some other cases, another definition is used [2] (without weights):

$$F = H(sensitivity, 1- specificity)$$

Where H is harmonic mean.

Reference: