Data
main topic 

To create a G chart, you can record your data in one of the following ways:

·  Dates of events

·  Number of opportunities between events

·  Number of opportunities until an event

Dates of events

When your data are entered as dates, Minitab calculates the number of days between events and plots each value on the G chart. When you use dates, you should verify that the number of possible opportunities per day is fairly constant.

Number of opportunities between or until an event

You can record either the number of opportunities between events or the number of opportunities until an event occurs.

Suppose infections occurred in the 4th, 16th, 27th, 50th, and 80th patient in an emergency room. If you record the number of patients between events, the data are shown below in the Between column. If you record the number of opportunities until an event, the data are shown below in the Until column.

If your data are recorded as the number of opportunities until an event, Minitab subtracts 1 from each value to convert the data to number of opportunities between events and plots the converted values on the G chart.