II. Probability and Statistics for Reliability
A. Basic concepts
4. Poisson process models (Understand)
Define and describe homogeneous and non-homogeneous Poisson process models (HPP and NHPP)
Do you have a trend or not?
Additional References
Laplace’s Trend Test (article)
Quick Quiz
Hi Fred,
Is the LaPlace trend test only for repairable systems? Or could I use this to see if a particular part in a population of systems has an increasing failure rate? Sort of another approach to fitting a Weibull and looking at the shape parameter.
Hi Raye, good question. I think you can use it as suggested. I would also explore using the Mean Cumulative Function. A plot of number of failures over time graphically (and there are analytical methods) can likewise detect a trend to arrival rate of failrues.
Using parametric tools tends to be a bit more powerful – meaning they can detect smaller shifts or changes with less data. Yet, non-parametric approaches can handle cases when we want a consservative approach and we either know the underlying distribution is complex or is totally unknown.
Cheers,
Fred