•How many times was the target disorder absent?:b+d
•How many of these times did the diagnostic test produce negative results?:d
not count the number of times the diagnostic
test produced negative results when the target disorder was present (c). We are only interested in the cases where the target disorder was absent.
•So what fraction of the total number of times the target disorder was absent did the diagnostic test produced negative results?:b/(b+d)