Let me ask you something concerning MTBF Do make compromises around gathering and analyzing data since you only need to report MTBF? Do you use MTBF (exponential distribution) based test planning when you know the product has a non-constant hazard rate? These questions came up this week via email looking for advice when directed to … Continue reading A Couple of Questions for You Concerning MTBF
REVIEW: Analyzing Repairable System Failures Data Recently, Ziad let me know he published an article titled Analyzing Repairable System Failures Data in the April-May 2017 issue of Uptime magazine (subscription required). He suggested I’d be interested in the article since it provides a way to analyze repairable system data without using MTBF. He was right. The … Continue reading REVIEW Analyzing Repairable System Failures Data
Illuminating MTBF’s Lack of Information Here’s a simple illustration of how MTBF oversimplifies data concealing essential information. By convention, we tend to use MTBF for repairable data. That is fine. You may also be aware of my dislike for the use of MTBF, for many different reasons. If you find yourself suggesting your organization, customer, … Continue reading Illuminating MTBF’s Lack of Information
Plot the Data Just, please, plot the data. If you have gathered some time to failure data. You have the breakdown dates for a piece of equipment. You review your car maintenance records and notes the dates of repairs. You may have some data from field returns. You have a group of numbers and you … Continue reading Plot the Data
What can you do if everyone across you industry is using MTBF? First, stop using MTBF yourself. Second, show others the information that is found in using Reliability directly rather than using MTBF. Third, translate your work back to MTBF and be very clear about duration and other assumptions.
MTBF is often used in textbooks with only a mention of other tools and calculations. Here are a few possible reasons.
A table of numbers is not information, it is data. It is information that we need to make decisions, to notice differences and to detect patterns.
A friend and colleague brought a thesis paper by Louis J Hogge to my attention. Titled “Effective Measurement of Reliability of Repairable USAF Systems, the document proceeds to recommend the US Air Force to stop using MTBF and related measures and instead to use Mean Cumulative Functions (MCF) instead.
There are Alternatives to using MTBF Just a quick note this week to pass along a message from Michael. He’s conducted a bit of research on Mean Cumulative Function and found a few papers. And, according to Michael’s request I’m working on a short introductory tutorial for those new to MCF.
With the kind permission of Wayne Nelson and Robert Abernathy we are posting an article on the analysis of repair data. As you may know, the assumptions made when using simple time to failure analysis of repairable systems may provide misleading results. Using the analysis method outlined by Wayne is one way to avoid those … Continue reading Graphical Analysis of Repair Data