Table 1.

Frequencies (n) and proportions (% or per 1000 readings) of readings, true positive (TP), false positive (FP), true negative (TN), false negative (FN), sensitivity of the radiologists ($\frac{\mathit{TP}}{\mathit{TP}+\mathit{FN}})$, and specificity ($\frac{\mathit{TN}}{\mathit{TN}+\mathit{FP}}$) of the radiologists for each category of image position

Image position	Readings		True positive		False positive		True negative		False negative		$\frac{\mathit{TP}}{\mathit{TP}+\mathit{FN}}$	$\frac{\mathit{TN}}{\mathit{TN}+\mathit{FP}}$
	n	%	n	Per 1000	n	%	n	%	n	Per 1000	%	%
1–3	210,425	7.2	1510	7.2	13,676	6.5	195,128	92.7	111	0.53	93.2	93.4
4–16	715,021	24.3	3084	4.3	34,800	4.9	676,748	94.7	389	0.54	88.8	95.1
17–33	648,840	22.1	2616	4.0	28,506	4.4	617,355	95.2	363	0.56	87.8	95.6
34–66	692,092	23.6	2724	3.9	28,195	4.1	660,735	95.5	438	0.63	86.2	95.9
> 66	670,934	22.8	2530	3.8	23,241	3.5	644,671	96.1	492	0.73	83.7	96.5
Total	2,937,312	100.0	12,464	4.2	128,418	4.4	2,794,637	95.1	1793	0.61	87.4	95.6