# Mean of fluorescence in FlowJo - (Apr/18/2014 )

Dear colleagues,

I'd like to know how to calculate the mean of fluorescence per cell by flow cytometry.

I'm just measuring the total amount of DNA in one wt cyanobacteria spp, and comparing with the total amount of DNA with a modificated strain that is suposed to have more DNA (so I should detect more DNA per cell). I'm using SYBR green.

So, I just would like to compare the mean of fluorescence (SYBR) per cell in both strains. I just need relative units (for example, if mutant have double amount of DNA than wt).

In Flow Jo there is a tool called "mean". You can apply this statistic to a particular fluorescence (I understand that this means: mean of fluorescence/cell)

Does anyone know if I can just use that measurement for the publication? Or should I normalize this value somehow? Not sure...

Easy rule of thumb.

If your population is normally distributed, "Mean" means the arithmetic mean, and assumes a Gaussian distribution.

If you're looking at a non-normally distributed population - a population curve that shows asymmetry on histogram, or a pronounced shoulder - use the geometric mean.

For more specific detail, you can consult a professional statistician - many larger institutions will have stats consulting core groups. But their tendency will be to overcomplicate your analysis.