After a discussion with a client this morning, and their motor vendor’s reliability engineer asked for a reference for a sample size calculation formula I recommended, I had a short email exchange with said reliability engineer. In my note with the references, I included an aside with a link to this site. He liked the site and agreed that MTBF was often misunderstood and not useful. He asked if the store sold much in the way of NoMTBF logo’ed merchandise – it doesn’t btw. I thought about how and why this site and the store exist and that invited my passion on this topic once again.
We need to do something to further the eradication of MTBF.
First, I suspect the ASQ CRE body of knowledge is coming up for review. Here are some ideas on what we can do to ‘fix’ the BoK.
Create a petition and submit to ASQ Certification Board with recommendation to drop the mention and emphasis related to MTBF.
- Encourage those that understand the proper use of MTBF to be on the team that rewrites the BoK – i.e. stack the deck.
- Barring the above, establish a boycott of the CRE BoK and certification process – i.e. not send them renewal fees or sit for the exam until it is ‘useful’.
Next, let’s consider standards. They often govern how our peers and colleagues think about reliability. If the standard relies on the assumptions related to MTBF, it should change. I am on the IEC group related to durability and regular lobby the group to drop, minimize or modify any use of MTBF. It is a slow process. I’m sure you may either use or be on standards teams that also use MTBF (and shouldn’t). So, what can we do here? Here are some ideas.
Work from within the standards writing framework to rework the standards.
- We should list ‘offending’ standards and publicize the effort.
- We can again create petitions and send to standard’s bodies to encourage the wholesale rewriting of ‘offending’ standards.
Product data sheets often use MTBF or Life (with determination of ‘Life’ being the unbiased estimator for the single parameter of the exponential distribution). As anyone reading this far down in this blog knows, that is a signal to any reliability progressional to ask the vendor to fully explain what the mean and to ask for additional information, data, or justification of claimed values. How about we just insist they don’t use MTBF. Again, what can we do? This a much larger issue with literally thousands of authors of data sheets. Here are some ideas.
Hold up a few as examples of being a really bad practice.
- Start a letter writing (email) campaign to vendors with ‘offending’ data sheets to increase awareness of their faulty practice, and that we are watching, want improvement and are available to help with education materials (i.e. this site).
- Write to company CEO’s and expose the mis information their teams or listing on data sheets.
This is just a place to start, to actually do more than simply discuss the issue amongst ourselves. I’m certainly open to more ideas and areas to press for change. New congressional bill and eventual law, new regulatory requirements, lawsuits (class action?), Superbowl advertisement, … What are you ideas, which do you like, what can you help to make happen?