Example of Laney P' Chart
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The records management staff at a small hospital improved the accuracy and completeness of patient records. To sustain these improvements, the staff tracks the number of incomplete and inaccurate records that are filed each day.

The number of records is high, with an average subgroup size of more than 2500. The data exhibit a large amount of overdispersion (see Example of P Chart Diagnostic). The staff decides to use a Laney P' chart instead of a traditional P chart to monitor patient records.

1    Open the worksheet DEFECTIVERECORDS.MTW.

2    Choose Stat > Control Charts >Attributes Charts > Laney P'.

3    In Variables, enter Defectives.

4    In Subgroup sizes, enter 'Total Records'. Click OK.

Graph window output

Interpreting the results

The number of incomplete records appears to be stable. No patterns appear in the data. No points are out of control.

To see the same data plotted on a traditional P chart, see Comparing traditional P charts and Laney P' charts.