Quality and Process Methods • Control Chart Builder • Statistical Details for the Control Chart Builder Platform • Control Limits for u-charts and c-charts
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Control Limits for u-charts and c-charts
The lower and upper control limits, LCL, and UCL, are computed as:
u-chart LCL =
u-chart UCL =
c-chart LCL =
c-chart UCL =
The limits vary with ni.
ui is the number of nonconformities per unit in the ith subgroup. In general, ui = ci/ni.
ci is the total number of nonconformities in the ith subgroup
ni is the number of inspection units in the ith subgroup
u is the average number of nonconformities per unit taken across subgroups. The quantity u is computed as a weighted average
N is the number of subgroups

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Help created on 7/12/2018