As far as I know, CFU counts from bacterial suspensions should approximately follow a Poisson distribution. So in order to perform a One-way Anova, a mathematical transformation to achieve normality should be done. Am I correct on this? And which transformation would be ideal in this case? .
My issue is to compare means of colony forming unit counts from 3 groups of 8 mice. Each group has a different genotype. Shapiro-Wilks test for normality showed that the counts do not follow a normal distribution.
Thank you very much.
At least some of my counts are very large (mean counts for the three different groups are: G1: 337150; G2: 43000, G3: 16536000. However, I am unsure wether Poisson regression may be performed on counts this large.
The variance of the samples is huge (2.28397E+10^11; 4102357143; 9.29586E*10^14). This would constitute over dispersion, am I correct?