Calculating standard deviation from histogram 1

[dgallup]

I have data in a histogram format that I want to calculate the standard deviation. See the attachment.

Any ideas short of reentering all 656 values in a column? Must be a better way.



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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[MintJulep]

Short example:

Thickness 1, count = 2
Thickness 2, count = 3
Thickness 4, count = 5

Average = [(1*2) + (2*3) + (4*5)]/(2+3+5) = 2.8

STD = sqrt( [2*(1-2.8)^2 + 3*(2-2.8)^2 + 5*(4-2.8)^2]/(2+3+5))

I think.

 

[dgallup]

That gave me 3.31 which "looks close".

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[IRstuff]

You don't need to enter all the numbers, just the numbers in the last column, so I did that for you:

http://files.engineering.com/downlo...ac-9f24-49e1-84ff-c1b19de05418&file=stdev.xls

which matches dgallup's answer



TTFN
faq731-376

 

[dgallup]

Right, I just used the last column. Thanks for the confirmation.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.