Data - Growth Curves
main topics 

The data you gather for parametric and nonparametric growth curves are the failure times for a repairable system. For example, an automobile breaks down, is repaired and put back into service, then breaks down again, etc. The data points represent the time of each failure without taking into account the repair time. In other words, the analysis is done as if the system instantaneously works again after failing.

This table describes the types of observations you can have.

Type of observation

Description

Example

Exact data

You know exactly when each failure occurred

The engine failed at exactly 500 days, was repaired, then failed at 825 days

Interval data

You only know that each failure occurred between two particular times

The engine failed sometime between 475 and 500 days, was repaired, and then failed again sometime between 675 and 725 days

How you set up your worksheet depends, in part, on the type of data you have:

·    When your data consist of exact failure times, see Growth curves - exact data.

·    When your data consist of failures within intervals and you are using nonparametric growth curves, see Growth curves - interval data or Growth curves - grouped interval data.

·    When your data consist of failures within intervals and you are using parametric growth curves, see Growth curves - interval data.

Note

Stack the system failure time data together if you believe that the rate of failures are identical, as in the case of identical manufacturing processes. Remember to include a system column in this case.