Table 2.

Frequencies (n) and proportions (% or per 1000 readings) of batches, readings, true positive, false positive, true negative, and false negative for each category of total batch size

Batch size	Batches		Readings		True positive		False positive		True negative		False negative
	n	%	n	%	n	Per 1000	n	%	N	%	n	Per 1000
1	5577	7.5	5577	0.2	266	47.7	655	11.7	4655	83.5	1	0.18
2–40	43,690	58.4	746,303	25.4	3654	4.9	39,929	5.4	702,313	94.1	407	0.55
41–72	13,582	18.2	733,345	25.0	3039	4.1	32,974	4.5	696,912	95.0	420	0.57
73–120	7846	10.5	720,030	24.5	2868	4.0	29,176	4.1	687,522	95.5	464	0.64
> 120	4073	5.5	732,057	24.9	2637	3.6	25,684	3.5	703,235	96.1	501	0.68
Total	74,768	100.0	2,937,312	100.0	12,464	4.2	128,418	4.4	2,794,637	95.1	1,793	0.61