The differential expression algorithm
Differential Expression for Single Cell performs Mann-Whitney U tests (also known as Wilcoxon rank-sum tests) for each feature.
If data is not normalized using Normalize Single Cell Data, the raw expression values are used. In this situation, results should be interpreted with caution, as differences could be solely driven by library size and other sample preparation specific factors.
When the data is normalized using Normalize Single Cell Data, the following corrected counts are used:
where
is the observed expression for the gene for a cell
that has total expression
.
is the target total corrected count, set to the median total expression of the cells used in the test. This leads to incomparable 'max group mean' values across different tests.
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The test is not performed for genes where the model fit has failed.
