Quality and Process Methods • Shewhart Control Charts • Statistical Details for the Control Chart Platform • Control Limits for EWMA Charts
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Control Limits for EWMA Charts
Control limits for EWMA charts are computed as:
LCL =
UCL =
where:
r is the EWMA weight parameter (0 < r ≤ 1)
xij is the jth measurement in the ith subgroup, with j = 1, 2, 3,..., ni
ni is the sample size of the ith subgroup
k is the number of standard deviations
is the weighted average of subgroup means
is the estimated process standard deviation

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Help created on 10/11/2018