Figure 4.

The probability of observing a cytopathic effect (CE) given in Eq. 12 as a function of the dilution number d and with Q = 1. (a) For D = 10, as the initial particle count N₀ increases, the critical dilution moves toward higher d. (b) Common dilution factors include logarithmic dilution (D = 10), half-logarithmic dilution (D = 10^1/2), and quarter-logarithmic dilution (D = 10^1/4). Logarithmic dilution requires a lower number of dilutions to cause the characteristic decrease in probability, requiring less individual assays to perform. Quarter-logarithmic dilution, though requiring more dilutions, has a slower transition from high to low probability across d, making the assay less sensitive to experimental error or noise. The plot above can be used to quantify the tradeoffs between the choices of D.