Control Charts

Control charts are graphical tools used to monitor process variation over time. Variables charts (X̄-R, X̄-S, I-MR) are used for continuous data. Attributes charts (p, np, c, u) are used for discrete data. X̄-R charts monitor the process mean (X̄) and range (R). The p-chart monitors the proportion of nonconforming items. Control charts distinguish between common cause and special cause variation.

Governing FormulaX̄ chart: UCL = X̄̄ + A₂R̄, LCL = X̄̄ - A₂R̄; R chart: UCL = D₄R̄, LCL = D₃R̄

Knowledge Check

10 Questions

1.Which control chart is used for monitoring the process mean?

2.A p-chart is used for:

3.What is the purpose of an R-chart?

4.Which control chart is used for count of defects per unit?

5.What is the difference between a c-chart and a u-chart?

6.The np-chart is similar to the p-chart but uses:

7.In an X̄-R chart, the X̄ chart monitors:

8.What is the I-MR chart used for?

9.Which control chart is most sensitive to small shifts in the process mean?

10.The control limits for a p-chart are calculated as: