Once we have the sample mean and standard deviation, we can calculate the upper control limit as shown in Eq. 3. We can signal an alarm if the actual count exceeds the upper control limit, and the larger the amount by which we exceed the upper control limit, the greater the severity of the alarm. The alarm level is defined as the probability of seeing the count Xi or a lesser count under the assumption that the observations are distributed according to a normal distribution with mean I and standard deviation 6. In Eq. 4, the symbol O refers to the
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