I do not think the method of interpolation differs depending on the
The following is what I inferred from one example some months ago. I
hope it helps.
Consider the following 20 values in A1:A20:
Compute the 85%percentile.
Excel's PERCENTILE(A1:A20,85%) results in 9.15.
It appears that Excel calculates that as follows (p =3D percentile):
i =3D 1 + INT((20-1)*85%) =3D 17
f =3D MOD((20-1)*85%,1) =3D 0.15
p =3D INDEX(A1:A20,i) + f * (INDEX(A1:A20,i+1) - INDEX(A1:A20,i))
PS: For broader participation, you might want to post future
inquiries using the MS Answers Forums at
it is not that I like that forum. it is just that MS has ceased to
support the Usenet newsgroups. Hence, participation here is limited
to the sites that share a common newsgroup mirror, which is no longer
centralized at MS.