Excel: PERCENTILE.INC(A1:A5,0.2) = 1.6
Steps:
1. a = 0, 2, 3, 4, 5
2. percent = 0.2
3. n = 5
4. k = TRUNC(percent * (n – 1) + 1) = TRUNC(0.2 * 4 + 1) = TRUNC (1.8) = 1
5. f = percent * (n-1) – TRUNC(percent*(n-1)) = 0.8 – TRUNC(0.8) = 0.8
6. output = a[k] + (f*a[k+1] – a[k]) = a[1] + (0.8 * a[2] – a[1])
= 0 + (0.8 * (2 – 0)) = 1.6
Reference: http://support.microsoft.com/default.aspx?scid=kb;en-us;Q103493