Data considerations for Z-MR Chart

To ensure that your results are valid, consider the following guidelines when you collect data, perform the analysis, and interpret your results.

The data should be continuous

If your data are counts of defectives or defects, use an attribute control chart, such as P Chart or U Chart.

The data are collected from a short-run process

If your data are not from a short-run process, use Xbar-R Chart or Xbar-S Chart for data in subgroups or I-MR Chart for individual data.

The data should be in time order

Because control charts detect changes over time, the order of the data is important. You should enter the data in the order it was collected, with the oldest data at the top of the worksheet.

The data should be collected at appropriate time intervals

Collect data at equally spaced time intervals, such as every hour, every shift, or every day. Select a time interval that is short enough that you can identify changes to the process soon after the changes occur.

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