Growth curves - grouped interval data
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Grouped interval data works like interval data except that, instead of a system column, you have a column containing the number of systems.

Enter your data in table form, using Start and End columns:

·    Start - the time at the start of the interval.

·    End - the time at the end of the interval.

·    NSystems - the number of systems running at the beginning of each interval.

·    Cost - the total cost of repairs in a particular interval.

This data set illustrates tabled data with a cost column.

In this example,

·    Ten systems are running at 0 hours. Between 0 and 5 hours of operation, 8 repairs were made to these systems.

·    Four systems are left running after the final observation time of 15 hours.

When you have more than one sample, you can use separate columns for each sample. Alternatively, you can stack all the samples in one column, then set up a column of grouping indicators. For an illustration, see Stacked vs. Unstacked data.

Each sample is analyzed independently and results in one growth curve. All the samples display on a single plot, with different colors and lines to help you compare reliability growth between samples.

For general information on repairable systems data, see Data - Growth Curves.