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The error for a single peak is calculated as when partially replicated spectra are collected, and these are again averaged to give a single error per replicated spectra set. <br>
However as all replicated spectra sets will have their own error estimate, variance averaging across all spectra sets will not be performed.
=== Peak volumes with baseplane noise RMSD ===
The method of error analysis when no spectra have been replicated and peak volumes are used is highly dependent on the integration method. <br>
Many methods simply sum the number of points within a fixed region, either a box or oval object. The number of points used, $N$, must be specified by another user function in this class. <br>
Then the error is simply given by the sum of variances:
$$\sigma_{vol}^2 = \sigma_i^2 * N $$
where $\sigma_{vol}$ is the standard deviation of the volume, $\sigma_{i}$ is the standard deviation of a single point assumed to be equal to the RMSD of the baseplane noise, <br>
and $N$ is the total number of points used in the summation integration method. For a box integration method, this converts to the<br>
Nicholson, Kay, Baldisseri, Arango, Young, Bax, and Torchia (1992) Biochemistry, 31: 5253-5263 equation:
$$\sigma_{vol} = \sigma_i * \sqrt(n*m)$$
where $n$ and $m$ are the dimensions of the box.<br>
Note that a number of programs, for example peakint (http://hugin.ethz.ch/wuthrich/software/xeasy/xeasy_m15.html) does not use all points within the box.<br>
And if the number N can not be determined, this category of error analysis is not possible.
Also note that non-point summation methods, for example when line shape fitting is used to determine peak volumes, the equations above cannot be used. <br>
Hence again this category of error analysis cannot be used. <br>
This is the case for one of the three integration methods used by Sparky (http://www.cgl.ucsf.edu/home/sparky/manual/peaks.html#Integration). <br>
And if fancy techniques are used, for example as Cara does to deconvolute overlapping peaks (http://www.cara.ethz.ch/Wiki/Integration), this again makes this error analysis impossible.
=== Peak volumes with partially replicated spectra ===
When peak volumes are measured by any integration method and a few of the spectra are replicated, <br>
then the intensity errors are calculated identically as described in the `Peak heights with partially replicated spectra' section above.
=== Peak volumes with all spectra replicated ===
With all spectra replicated and again using any integration methodology, the intensity errors can be calculated as described in the `Peak heights with all spectra replicated' section above.
== See also ==
[[Category:Analysis]]