Question: MAGeCK vs MWU CRISPR Screen Tests
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gravatar for Scott McKay
6 weeks ago by
Scott McKay20
Scott McKay20 wrote:

Does anyone know the differences between the MAGeCK analysis and Mann-Whittney U Test for CRISPR screens? I'm not well versed in statistics and am looking for some insights. Thanks!

statistics rna-seq analysis • 112 views
ADD COMMENTlink modified 6 weeks ago by dsull1.5k • written 6 weeks ago by Scott McKay20
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gravatar for dsull
6 weeks ago by
dsull1.5k
UCLA
dsull1.5k wrote:

MAGeCK uses a parametric statistical test which means that it makes assumptions about the distribution of the data (to be technical: MAGECK models guide RNA counts using a negative binomial distribution). Another example of a parametric test is the Student's t-test.

Mann-Whitney U test is a non-parametric test. This means it doesn't make assumptions about the distribution of the data. In the case of Mann-Whitney U tests, it basically gets you p-values by rank ordering (see https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test#Illustration_of_calculation_methods ). Consider the following. Situation A: Your treated group has values 7,8,9 and your control group has values 1,2,3. Situation B: Your treated group has values 7000, 8000, 9000 and your control group has values 1,2,3. In both situation A and situation B, the p-value is the same when you run a Mann Whitney U-test. Why? Because the rank ordering is the same! Nonparametric tests are generally considered to be less powerful than parametric tests (look up "statistical power" if you're not sure what that means).

ADD COMMENTlink written 6 weeks ago by dsull1.5k
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