I have two different data frames , one per condition, where each one of them has 3 columns:

specie : a qualitative value

population@4days : population calculated for that specie at 4 days

population@12days : population calculated for that specie at 12 days

Using basic calculations I have computed the growth rate for each population and now I want to compare the two distribution of rates ( I am interested in a global conclusion, not specific for each specie)

My question is if I need to normalize to correctly compare them. The number and species in each one is different and the sum of population is also different between all of them.

If I have to, which will be the best way to normalize and compare them?

Thank you in advance for your consideration.

if I get your question right you are asking how to (if) normalize and compare the populations at 4 vs. 14 days, is that correct?

if so, do you have a day 0? that would be your initial point where to normalize that data to.

how many samples do you have per each time point?

do you need/want to do 0 vs. 4; 0 vs. 12; 4 vs. 12?

also, population of...?..minions?

Yes! That is correct, is a global comparison of growth for different bacterial populations exposed to two different conditions and data collected at 4 and 12 days. I don't have a time 0 but I have 2 replicas per time for each condition (2 conditions, 2 times, 2 replicas each one).

The comparison tries to define is one of the conditions allows a better general growth for the mixed population.