Need the correct percentile formula

[Cherrie]

I am trying to compute the 10th precentile for MGMA benchmark data. I don't have the dataset; however, I have the following information.

n value=104
# of departments=14
Mean= 8448
A1: Standard Deviation =3,438
B1: 25th Percentile=6,170
C1: 50th Percentile=7,772
D1: 75th Percentile=10,651
E1: 90th Percentile=13,193

According to MGMA, the 10th percentile is 4,589. However, when I use the =Percentile.INC(A1:E1,.10) excel 2010 formula, it calcualtes it to be 4,531. In the ballpark.... but not the exact answer. Is there a more precise formula? Please help. I've tried everything.

Thanks

 

[scottylad2]

My Percentile worked out using a formula is in I3, and using the inbuilt Percentile.Inc formula returns a similar, but not exact result. I suspect there's extra decimals along the way that are having a slight effect on the result

Excel Workbook
	E	F	G	H	I
2	Scores	My Score	Count of Scores	Scores	Percentile
3	447	2750	27	6	0.22
4	1125	2770.08
5	1272
6	2081
7	2509
8	2562
9	2851
10	2952
11	3315
12	3355
13	3736
14	4248
15	4263
16	4632
17	4659
18	4979
19	5031
20	5256
21	5487
22	5736
23	6277
24	6505
25	6512
26	6867
27	7081
28	7418
29	7490
Sheet1

Usingthe inbuilt formulas answer in the same formula places the answer in the same percentile 0.22

 

[Cherrie]

Thanks, the formula does gets me within the percentile, but I suspect there is a formula that will be more precise with the answer I've provided. I just don't know what is missing. Again, I don't have the data used to get to the info already given. This is all I have to work with. Thanks again.

 

[scottylad2]

Wthout all the dataset too much is gueeswork. Your Mean or SD don't really say anything about the data. The percentile you are showing is almost certainly covering more than one number that will fall within the 10th percentile range.

Loosely, pick a number from your range, workout how many numbers from within your dataset are below that number and divide THAT number by the total number in the dataset to get the percentile for that number.

Without all the other numbers you can't be precise, the percentage change shown by the SD doesn't help nor does the Mean

 

[Cherrie]

Ok. Thanks for responding. I appreciate it.