Example of G Chart
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A hospital wants to monitor the number of post-surgical infections to ensure that the rate of infection remains low over time. Hospital staff record the date of each post-surgical infection. Because this data is rare event data, the staff use a G chart to track the rate of infections.

1    Open the worksheet INFECTIONS.MTW.

2    Choose Stat > Control Charts > Rare Event Charts > G.

3    From Form of Data, choose Dates of events.

4    In Variables, enter 'Date of infection'.

5    Click OK.

Session window output

G Chart of Date of infection

 

 

 

Test Results for G Chart of Date of infection

 

 

Benneyan Test. 3 points in a row equal to 0.

Test Failed at points:  30, 31

 

* WARNING * If graph is updated with new data, the results above may no

          * longer be correct.

Graph window output

 

Interpreting the results

Observations 30 and 31 failed the Benneyan test because 3 points in a row are equal to 0. The staff recorded 3 or more infections on the same day. The data analyst examines the worksheet and observes that hospital staff recorded five infections on October 26.