If k is zero or blank, percentile rank of 1/(n – 1) returns the smallest value. If zero, it is out of range and an error is returned.
If k is nonnumeric or outside the range 0 to 1, an error is returned.
If k is not a multiple of 1/(n – 1), PERCENTILEX.EXC will interpolate to determine the value at the k-th percentile.
PERCENTILEX.INC will interpolate when the value for the specified percentile is between two values in the array. If it cannot interpolate for the k percentile specified, an error is returned.