| Author |
Message |
    
Benoit Igne (benoit)
Member
Username: benoit
Post Number: 12
Registered: 11-2006
| | Posted on Friday, October 23, 2009 - 2:24 pm: | |
Howard,
Thank you for your answer. While assumptions might be difficult to meet with NIR data, the chi^2 approach might be the easiest way to get a first estimate of the error.
Benoit |
Howard Mark (hlmark)
Senior Member
Username: hlmark
Post Number: 279
Registered: 9-2001
| | Posted on Friday, October 23, 2009 - 2:03 pm: | |
Benoit - in principle, if the errors are really random, independent and Normally distributed, and the system is stationary (i.e., it's underlying behavior doesn't change with time - something very unusual in NIR!) then under those ideal conditions, the square of the SEP (and those other measures of error) will be distributed as chi^2, and there are statistical tables giving the confidence limits for the chi^2 distribution corresponding to different numbers of degrees of freedom and confidence levels. Then you could simply look up the confidence limits, multiply them by your SEP^2 and take their square root to get the confidence limits for your SEP.
I have to point out, though, that that is an awful lot of conditions for actual NIR data to meet. Don't forget, for example, that nonlinearity in the response introduces non-randomness and non-Normality, as does a simple skew of the model.
\o/
/_\ |
Benoit Igne (benoit)
Member
Username: benoit
Post Number: 11
Registered: 11-2006
| | Posted on Friday, October 23, 2009 - 1:25 pm: | |
Hello all,
I am trying to calculate an uncertainty value for my SEP but I would like to avoid having to perform a bootstrap type method.
Would you know of any simpler method to calculate confidence limits on an SEP or SEC or SECV?
Thank you for your help,
Ben |
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