Hi -

Hoping I can get some opinions on the method we are using to calculate percentiles.

I work with a small non-profit - I need to calculate percentiles for a number of fee ranges, i.e. what is the median fee charged, 45th ptile, 55th ptile etc. in different regions of our state.

We have been calculating percentiles as follows:

- rank order all the fees from low to high

- locate the integer of the p*nth record (e.g. if the desired ptile is the 45th then go to the record number that is the integer portion of .45*total records)

- If the record number is even take that record value as the pth ptile.

- if the record number is odd go to the next higher number, take the average of the two values and call that the pth ptile.

I recently compared the results of the above to the results of calculating the ptiles in excel using the excel percentile function. Mostly there was no difference in results but in the smaller data sets there were differences. I know that there are several methods for calculating ptiles. Is the above method okay? How might it be improved?

Thanks for any help!!!

Hoping I can get some opinions on the method we are using to calculate percentiles.

I work with a small non-profit - I need to calculate percentiles for a number of fee ranges, i.e. what is the median fee charged, 45th ptile, 55th ptile etc. in different regions of our state.

We have been calculating percentiles as follows:

- rank order all the fees from low to high

- locate the integer of the p*nth record (e.g. if the desired ptile is the 45th then go to the record number that is the integer portion of .45*total records)

- If the record number is even take that record value as the pth ptile.

- if the record number is odd go to the next higher number, take the average of the two values and call that the pth ptile.

I recently compared the results of the above to the results of calculating the ptiles in excel using the excel percentile function. Mostly there was no difference in results but in the smaller data sets there were differences. I know that there are several methods for calculating ptiles. Is the above method okay? How might it be improved?

Thanks for any help!!!

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