what is the mean of "deviation" in fastqc?

[hohosharon]

Hi:
I have a question from http://www.bioinformatics.bbsrc.ac.u...20Content.html
I don't know what is the mean of "deviation" on GC distribution over all sequences.
Can u give me definition of deviation ?
Thanks.

[dpryan]

Wikipedia has a convenient definition of deviation. You can also read the article on standard deviation, for which there are translations in many languages.

[hohosharon]

The sum of the "deviations" from the normal distribution represents more than 15% of the reads.

I think here's "deviations" maybe is not the same mean of "standard deviations".
I guess here's "deviations" is the difference of C count per read and Theoretical Distribution, so i want to check what is the mean of "deviation" in here.
thanks

[fkrueger]

This module tests how closely the observed GC distribution curve resembles a modeled normal distribution with the same overall GC content as found in the sample. If they deviate, i.e. are different, more than 15%, FastQC will throw a warning.