Hi,
In your example code/chapter3/solutions/percentile_score.py you have following code:

    if percentile == 0:
        return data[0]
    elif percentile == 100:
        return data[-1]

so for percentile == 0 it will return 1 and for percentile == 100 it returns 14
However based on the link that you provided Calculating Percentiles
percentile for 1 should be 7.1 and for 14 it should be 92.9
I checked other web sites and they all have different logic but most of them accept percentile from 1-99. 0 and 100 are invalid numbers.
So is there an error in your code?