Data considerations for T 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 the specific date and time of each rare event or the specific amount of time between rare events

If your data are the dates of each rare event but not the specific time for each event, use G Chart.

The data should follow a Weibull or exponential distribution

If the data do not follow a Weibull or exponential distribution, use a variables chart, such as Xbar-R Chart or Xbar-S Chart.

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.