Table 2.

${\mathrm{ARL}}_1$ of Shewhart-type schemes with approximate and exact control limits, with n = 1, $\gamma =(0.3,0.3,0.3)$ and ${\mathrm{ARL}}_0=370$.

	$\rho =(-0.4,-0.4,-0.4)$		(0.0, 0.0, 0.0)		(0.4, 0.4, 0.4)		(0.8, 0.8, 0.8)		(0.4, 0.6, 0.8)
τ	exact	appro	exact	appro	exact	appro	exact	appro	exact	appro
1.00	371.7	371.7	368.8	367.8	369.9	370.8	369.1	373.5	369.8	372.6
1.05	313.0	313.0	324.1	325.4	339.7	340.3	336.1	355.7	282.5	280.8
1.10	255.5	255.5	274.5	275.2	294.5	295.3	307.7	322.9	197.5	199.0
1.20	167.3	167.3	193.2	189.9	221.2	222.8	215.2	244.2	81.8	81.4
1.30	107.7	107.7	128.1	128.2	151.6	158.1	140.8	167.9	30.3	31.3
1.40	67.7	67.7	86.6	85.4	104.0	108.3	85.7	107.9	12.7	12.7
1.50	46.4	46.4	57.7	56.8	69.2	72.7	49.5	63.1	6.1	6.1
1.60	32.1	32.1	39.7	39.9	46.9	48.7	28.2	36.2	3.5	3.5
1.80	17.6	17.6	20.2	20.5	22.5	23.3	9.3	12.3	1.8	1.8
2.00	10.5	10.5	11.9	11.7	11.9	12.2	3.8	4.8	1.3	1.3