The dilution factor is a number used for getting the whole number of infected cells from the observed data. For a testing assay used a half dilution, at each time point the half medium is taken out from the culture for counting and then thrown away. The observed data is the data from the half volume. So, the total infected cells in the initial culture shall be 2 times of the observed data. Then the dilution factor is 2. The calculation model here is always based on the total number of infected cells regarding of the initial culture. Several examples about the dilution factor are given as follows,
Remeber the above case is different from the case of the observations at Day 3, 5, and 6, which is not a missing data case and the dilution factors are still 2, 4, and 8.