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tony_lincoln
USA
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 Posted - 01/30/2010 : 1:40:49 PM
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Hi,
I have one group data (16 numbers):
1
3
4
5
6
7
8
9
19
29
39
49
59
69
79
80
I wanna show this data in Origin with 25 and 75 percentile. The 25 percentile I calculated was 5.75, and 75 percentile was 51.5.
But in Origin, the 75 percentile was drawn at 5.5, the 75 percentile was drawn at 54.
So I wondered that my calculation was wrong, or the way to show the percentile box in Origin was wrong?
Thank you.
Tony |
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larry_lan
China
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Posted - 01/31/2010 : 9:56:11 PM
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Hi Tony:
Both Origin and Excel output the right result. The fact is, there are multiple methods to calculate percentiles. The default formula in Origin is Empirical Distribution with Averaging, while Excel use another formula to calculate it. Origin's default output is consistent with other statistical packages like SPSS, anyway, we can add the excel formula in later versions.
Thanks
Larry
OriginLab Technical Services |
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tony_lincoln
USA
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Posted - 02/01/2010 : 11:38:08 AM
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The calculation was not wrong in Origin. In Excel, R and other software, I can get the same result as Origin.
But the drawing and visualization in Origin were wrong:
the 25 percentile was drawn at 5.5, the 75 percentile was drawn at 54.
But Actually, the 25 percentile should drawn at 5.75, and the 75 percentile should be drawn at 51.5.
Thanks
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larry_lan
China
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Posted - 02/01/2010 : 11:05:44 PM
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Hi Tony:
I don't quite understand that you said "Origin get the same result like Excel, R. But drawing is wrong".
The below image is a box plot I created by our default options using your data. The report worksheet, is descriptive statistics calculated by "Statistics: Descriptive Statistics: Statistics on Column". While Graph1 is created from "Plot: Statistics: Box Chart".
You can see from the graph that the worksheet value for Q3 is consistent with the box plot. So, I think it's OK in Origin if the statistics result and plot are consistent.
However, I don't get the same result in Excel. Using the Excel function "PERCENTILE(A1:A16,0.75)", I can get value 51.5. As I mentioned above, we don't provide the method as Excel, and we can add that method in the future.
So, could you please tell me how do you calculate the percentile? Which Origin version you are using? Which patch? (You can see from "Help: About Origin") Why you said Excel, R and Origin generate the same results? Could you provide the R code?
If you have an OPJ explaining this, that will be great helpful if you can send us your OPJ. Or you can call our tech support team directly to discuss this issue (You can talk with Greg if you call).
Thanks
Larry
OriginLab Technical Services |
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Topic |
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25 and 75 percentile were not drawn well ?