Figure 3.

(a) Linearity and (b) precision across the dynamic range of ddPCR. (a) Red, green, and blue error bars denote the standard deviation of the Lambda DNA copy number per 20 μL of ddPCR for each of three independent gravimetric dilutions (estimated from n = 7 or 8 replicates in each case). The 95% confidence interval of the slope of the combined data is as indicated in the equation. (b) Each symbol denotes the stock Lambda DNA concentration (copies/μL) (estimated from n = 7 or 8 replicates for each of three independent gravimetric dilutions). Error bars represent the expanded uncertainty calculated by multiplying the combined standard uncertainty (eq 8) with a coverage factor of between 2.05 and 2.09 depending on the number of replicates in the independent gravimetric dilutions. This provides a level of confidence of 95% in the expanded uncertainty.