Question

Condition to be checked before calculating the control chart?

Answer 1

• Choose the appropriate control chart for your data.

• Determine the appropriate time period for collecting and plotting data.

• Collect data, construct your chart and analyze the data.

• Look for “out-of-control signals” on the control chart. When one is identified, mark it on the chart and investigate the cause. Document how you investigated, what you learned, the cause and how it was corrected.  

• Continue to plot data as they are generated. As each new data point is plotted, check for new out-of-control signals.

• When you start a new control chart, the process may be out of control. If so, the control limits calculated from the first 20 points are conditional limits. When you have at least 20 sequential points from a period when the process is operating in control, recalculate control limits.