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March 23, 2015


When I log transform my data during pairwise analysis why do my results change?


When I log transform my data during pairwise analysis on <i>GeneSifter Analysis Edition</i> why do my results change?

The log2 transformation takes place prior to performing the test, so the results will always differ with and without the transformation and depending on the data and the test the differences can be large.

If you are doing a statistical test on your data such as a likelihood ratio test you may notice differences in a pairwise analysis result. This is because the log transformation (log base 2) happens before the statistical test. This may be more dramatic on smaller datasets, low quality data, or groups of input data that are not equally distributed.


  1. It is most common to log transform data when performing a t-test.

  2. For NGS data, LRT(Likelihood Ratio Test) and Fisher's exact test, we do not recommend using log2 transformation feature.

  3. The LRT does not allow negative values and they are excluded.

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