29 days ago by
There is no need to cite simple statistics such as variance or Z statistics, however, you might consider median absolute deviation (MAD) as a robust alternative to variance, afaik this is commonly used as a filtering step in network analysis. If you do the filtering in R or another software, you can add a sentence like "all statistical analyses were done in R (R Core Team (2018))". You might also use other more advanced differential expression statistics like limma, DESeq2, etc. If you are using a particular package, you cite this package.
In general, there is no single best or authoritative way of filtering prior to downstream analyses.
In particular, I do not know what your intended downstream analysis is, so there is not much more I can recommend at this stage.
R Core Team (2018). R: A language and environment for statistical computing. R Foundation for Statistical
Computing, Vienna, Austria. URL https://www.R-project.org/.
Caveat: do not use FPKM, use CPM or TPM instead (this has been discussed here many times).