Fig 1. Visual representation of midSIN’s output for the example ED plate.

A: Illustration of the example ED plate where ${\mathcal{D}}_i$ are the chosen serial dilutions of the sample. For the example described in the text, ${\mathcal{D}}_1={10}^{-2}$, ${\mathcal{D}}_2={10}^{-2.5}$, …, ${\mathcal{D}}_{11}={10}^{-7}$, with 8 replicates per dilution. The number of infected wells (# inf) is indicated at the bottom of each dilution column. B: The midSIN-estimated posterior distribution of the log₁₀ infection concentration, log₁₀(SIN/mL), for the example ED experiment. The vertical lines correspond to log₁₀(SIN/mL), based on the most likely value (mode) of midSIN’s posterior distribution (solid blue), or computed from the RM (solid orange) and SK (dashed green) approximations of the log₁₀(TCID₅₀) (see Methods). The x-value of the white and light grey region on either sides of the mode indicate the edges of the 68% and 95% credible interval (CI), respectively. The midSIN-estimated log₁₀(SIN/mL) mode ± 68% [±95%] CI are indicated numerically above the graph. C: The number of infected wells (black circles) out of the 8 replicates, as a function of the 11 serial dilutions of the example ED plate, from the least (leftmost) to the most (rightmost) diluted. For example, x = 3.0 corresponds to a sample dilution of 10⁻³ or 1/1,000. The average (expected) number of infected wells, as a function of sample dilution, is shown for the most likely value of log₁₀(SIN/mL) (blue curve) or its 68% and 95% CI (inner and outer edge of the grey bands, respectively). The sample dilution (x-value) at which the blue curve crosses the horizontal dotted line (50% infected wells) corresponds to a concentration of 1 TCID₅₀ per ED well volume. The vertical lines indicate the sample dilution that yields a concentration of 1 TCID₅₀ according to the RM and SK approximations.