I am after some advice on analysing MIC data. We are testing the efficacy of a disinfectant and started with MIC to establish the working concentration of the product. This was done by carrying out a two fold dilution in a 96 well microtiter plate. This was repeated several times for each organism. I appreciate that the MIC is the lowest dilution that inhibits growth however as this test was replicated we have some bacteria such as Staphs that have different MICs on each plate! This data was from the same strain. Some colleagues have suggested taking the average and carrying out stats to get the range at 99% CI however as this is a two fold dilution it is obviously quite large as the concentration of disinfectant in each well is halved each time. Can averages be taken for MICs like this? What stats can I use to analyse this data?