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Fig. 1 | BMC Medical Research Methodology

Fig. 1

From: Sense and sensibility: on the diagnostic value of control chart rules for detection of shifts in time series data

Fig. 1

Example control charts. a random variation. b Non-random variation caused by a large, possibly transient, shift in data identified by one data point being outside the upper control limit. c Non-random variation caused by a sustained moderate shift in data identified by an unusually long run of 13 data points below the centre line (Western Electric rule 4 and Anhoej rule 1) and unusually few crossing (Anhoej rule 2)

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