Table 3.

Comparison between the certified copy number concentrations and concentration estimated by ddPCR in the ERM-AD623 series. A droplet volume of 0.91 nL has been used to calculate the copy number concentration

ERM-AD623	Certified value (cp/μL)	U CRM	Average measured values (cp/μL), n = 8	stdev	Δ m (cp/μL)	u m (cp/μL)	U Δ (cp/μL)	Significant bias	% difference
f	10	1.5	9	2	1	1	2	No	12
e	104	10	87	10	17	7	14	Yes	16
d	1020	90	846	80	174	60	121	Yes	17
c	10,300	1000	8851	669	1449	602	1203	Yes	14
b	108,000	11,000	90,951	8105	17,049	6832	13,663	Yes	16
a	1,080,000	130,000	908,543	58,766	171,457	71,333	142,665	Yes	16

The calculated bias is significant with a confidence level of 95 %

U _CRM expanded uncertainty of the certified value; Δ _m absolute difference between mean measured value and certified value; U _Δ combined uncertainty of result and certified value; u _m uncertainty of the measurement result, calculated as the standard deviation divided by the square root of the number of replicates