Volume per period: | 30 | 50 | 100 | 200 | 500 | |||||||
Baseline event rate | Absolute shift | OR | In-control ARL | Out-of-control ARL | In-control ARL | Out-of-control ARL | In-control ARL | Out-of-control ARL | In-control ARL | Out-of-control ARL | In-control ARL | Out-of-control ARL |
1% | −0.5% | 0.5 | N/A* | N/A* | N/A* | N/A* | N/A* | N/A* | N/A* | N/A* | 61 000 | 5 000 |
+1% | 2.0 | 840 | 270 | 2 150 | 400 | 3 200 | 600 | 14 400 | 1 000 | 48 500 | 1 500 | |
+2% | 3.1 | 840 | 150 | 2 150 | 200 | 3 200 | 300 | 14 400 | 600 | 48 500 | 1 000 | |
10% | −5% | 0.5 | 2 700 | 330 | 6 150† | 500 | 14 600† | 500 | 38 800† | 600 | 1 15 000† | 1 000 |
+5% | 1.6 | 2190 | 270 | 5 850 | 400 | 9 800 | 400 | 29 000 | 600 | 94 500 | 1 000 | |
+10% | 2.3 | 2 190 | 120 | 5 850 | 150 | 9 800 | 200 | 29 000 | 400 | 94 500 | 1 000 | |
50% | −15% | 0.5 | 4 710 | 180 | 8 750 | 200 | 16 000 | 200 | 43 000 | 400 | 1 09 500 | 1 000 |
+15% | 1.9 | 4 710 | 180 | 8 750 | 200 | 16 000 | 200 | 43 000 | 400 | 1 09 500 | 1 000 | |
+25% | 3.0 | 4 710 | 60 | 8 750 | 100 | 16 000 | 200 | 43 000 | 400 | 1 09 500 | 500 |
*Lower-limits of chart are at zero so decreases cannot be detected.
†In-control ARLs for a chart set up to detect a decrease can differ from those for a chart set up to detect an increase because the exact binomial probability of crossing the upper limit will not always be the same as the exact binomial probability of crossing the lower limit.
ARL, average run length.