Ok, this is a "stupid" question that I probably should really know the answer to. I am researching bacterial invasion and replication within host cells, A. polyphaga to be exact. I grow the amoeba into a monolayer, add a certain number of bacteria to each sample, and allow them to incubate for 2 hours. This is done in duplicate. At two hours, I remove both sets of samples, remove the media from both, and wash the excess bacteria off gently. One set of samples gets media for the amoeba added and incubated for 46 hours (48 hours total). The first set of samples are washed and the amoeba lysed. The bacteria are serially diluted and plated to determine CFUs. The same is also done at 48 hours with the bacteria concentrated from the supernatant and lysed cells. My question is what calculations should be done to interpret what I am seeing. I will have multiple replicates by the end so everything will be averages eventually. I know one way to present this is just avg CFUs shown to indicate the amount of invasion and hopefully an increase with replication. It was also suggested that I divide the CFUs at 2 hours by the initial CFUs to show the percent that invaded...makes sense to me. I had been told that I should calculate the replication by taking the log of the CFUs at 48 hours divided by CFUs at 2 hours. What would that show? I assume they meant the log(CFUs 48/CFUs2). Any thoughts? Any suggestions with why you would recommend a certain way?