It's the rate of actual negatives that are perceived as positives. I make that mistake myself all the time, What helps me avoid it is this: you want a number t

It's the rate of actual negatives that are perceived as positives. I make that mistake myself all the time, What helps me avoid it is this: you want a number that is a property of the test method alone, independent of case distributions. A ratio between misidentified positives and identified positives (or true positives) would depend on sample distribution.