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第一节 常用控制规则
常用控制规则的符号和定义如下:
1 2s 1个控制测定值超过
±2s控制限。传统上,这是在Shewhart控制图上的“警告”限,用在临床检验也常作为Levey-Jennings控制图上的警告界限。见图15-1。
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图15-1 1 2s控制图
1 3s 1个控制测定值超过
±3s控制限。此规则对随机误差敏感。见图15-2。
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2 2s 2个连续的控制测定值同时超过
+ 2s或
-2s控制限。此规则主要对系统误差敏感。见图15-3。
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R 4s在同一批内最高控制测定值与最低控制测定值之间的差值超过4s。此规则主要对随机误差敏感。见图15-4。
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图15-2 1 3s控制图
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图15-3 2 2s控制图
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图15-4 R 4s控制图
3 1s 3个连续的控制测定值同时超过
+ 1s或
-1s。此规则主要对系统误差敏感。见图15-5。
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4 1s 4个连续的控制测定值同时超过
+ 1s或
-1s。此规则主要对系统误差敏感。见图15-6。
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图15-5 3 1s控制图
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图15-6 4 1s控制图
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图15-7
控制图
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7 T 7个连续的控制测定值呈现出向上或向下的趋势。见图15-8。
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图15-8 7 T控制图
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图15-9
控制图
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图15-10
控制图
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图15-11
控制图
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图15-12
控制图
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比例控制规则(m of n) L:如(2of3) 2S规则,即是连续的三个控制测定值中有两个控制测定值超过
+ 2s或
-2s控制限。见图15-13。此外还有(3of6) 2S规则。
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图15-13 (2of3)2S控制图