Use Nonparametric Growth Curve to analyze data from a repairable system, without making assumptions about the distribution of the cost or the distribution of the number of repairs. A repairable system is one in which the parts are repaired instead of being replaced when they fail. For example, automotive engines are usually repaired many times before being replaced.

The analysis uses nonparametric growth curves to estimate the mean cost of maintaining the system or the mean number of repairs over time. You can use the results to determine whether a trend exists in times between successive failures. For example, you can determine whether system failures are becoming more frequent, less frequent, or remaining constant. Growth curves chart the performance of repairable systems to help you establish the following:

- How often the system will require maintenance
- The number of replacement parts to have in inventory
- Whether the system is performing at an acceptable level
- Likely repair costs during the life of the system

For more information on growth curves, go to Estimating parameters for growth curves.

To perform a nonparametric growth curve analysis, choose

.To estimate growth curves of the mean number of repairs and the rate of occurrence of failure (ROCOF) over time using a power-law process or a homogeneous Poisson process, use Parametric Growth Curve.