Apdex Score

Apdex is a standardized performance-satisfaction score that sorts visits, relative to a time threshold, into satisfied, tolerating and frustrated groups and folds them into a number between 0 and 1.

Apdex's clever idea is to set aside the average and instead ask “what proportion of users had a good experience,” because an average buries a few very slow users under an acceptable-looking number. Its mechanic is a threshold T: a visit faster than T is satisfied, between T and four times T is tolerating, and slower is frustrated. But that same threshold is its weakness: the whole score is sensitive to the choice of T, and two teams with different T's get incomparable scores, so Apdex means something only when its threshold is explicit and fixed. Apdex's real value is in its philosophy rather than its exact formula: instead of an average, report the share of satisfied users.