PERCENTILE.INC
Read the distribution, not just the average.
Why planners need it
Averages hide pain. The 90th-percentile AHT or wait tells you what your tail looks like — which is what customers and SLAs feel.
Syntax
=PERCENTILE.INC(range, k) (k from 0 to 1)
Worked example
The AHT you’re under 90% of the time:
=PERCENTILE.INC(AHT, 0.9) → e.g. 410s while the mean is only 250s — a long tail your staffing must absorb.
Watch out: PERCENTILE.INC includes the endpoints; .EXC excludes them and needs >1/(n+1). For SLAs, agree which one your reporting uses.