The variance in expression levels of candidate reference genes, as indicated by the range of Ct values and SD, differed within a single treatment group. For example, within the control group at 6 h, the lowest variance in Ct values, as indicated by the lowest SD, was Actinb (SD = 0.18; Fig. 1a). The highest variance within the untreated group was for Mau2 (SD = 1.06; Fig. 1a). Interestingly, in some cases, genes differed in their expression variability, dependent upon the time point following LPS stimulation. For example, in the control group, at 6 h, the variance in Ct values between replicates recorded for the gene Rpl13a was larger (range(SD) = 26.15–27.96(0.91)) than the variance observed for Rpl13a at 24 h post-LPS stimulation (range(SD) = 25.86–26.17(0.17)).