Math, Statistics, and Engineering
In college, Mechanics was a required class from the civil engineering department. This included differential equation.
Luckily for me, I also enjoyed a required course called analytical mechanics for my physics degree. This included using Lagrange and Hamiltonian equations to derived a wide range of formulas to solve mechanisms problems.
In the civil engineering course, the professor did the derivation as the course lectures, then expected us to use the right formula to solve a problem. He even gave us a ‘cheat sheet’ with an assortment of derived equations. We just had to identify which equation to use for a particular problem and ‘plug-and-chug’ or just work out the math. It was boring. Continue reading Math, Statistics, and Engineering
The Dirge of the MTBF Bias
We use our biases every day to make choices.
We select the beige sweater because we have a color bias concerning our sweaters.
Many of our biases help us quickly make decisions. We rely on biases to move through the day. Many of our biases are under the surface, unconsciously guiding our daily decisions. Mostly, biases are good or at least inconsequential.
The problem is the bias that shields us from achieving our goals. Continue reading The Dirge of the MTBF Bias
Book Review: An Elementary Guide to Reliability
If you sort your Amazon search on ‘reliability engineering’ by price: low to high, you may find some interesting titles available for free or maybe a few pennies. Not one to resist a chance to fill another bookcase, it’s been a bit of spending spree.
One of the reasons, I am interested in older titles is to determine why MTBF is so prevalent today. So far, still looking and learning along the way.
There are many great books in our field. Sure, some are older. Some are not at all useful or helpful.
This book review is the first in what may become a monthly addition to the NoMTBF blog.
Today’s review is on the book, An Elementary Guide to Reliability (3rd) Third Edition, by G. W. A. Dummer and R. C. Winton. Continue reading Book Review: An Elementary Guide to Reliability
When Do Failures Count?
One technique to calculate a product’s MTBF is to count the number of failures and divide into the tally of operating time.
You already know, kind reader, that using MTBF has its own perils, yet it is done. We do not have to look very far to see someone estimating or calculating MTBF, as if it was a useful representation of reliability… alas, I digress.
Counting failures would appear to be an easy task. It apparently is not. Continue reading When Do Failures Count?
Sample Size and Duration and MTBF
If you have been a reliability engineer for a week or more, or worked with a reliability engineer for a day or more, someone asked about testing planning. The conversation may have started with “how many samples and how long will the test take?”
You have heard the sample size question.
Continue reading Sample Size and Duration and MTBF
Learn to Notice MTBF Everyday
Did you notice the speed limit signs in your neighborhood today?
If like me, you went about your commute or regular travels relatively blind. You watched for the neighbor’s dog that jumped into the road last week, yet didn’t register seeing the speed limit sign.
It’s a cognitive burden to notice the mundane or known. Continue reading Learn to Notice MTBF Everyday
The 3 Best Reasons to Use MTBF
This may seem an odd article for the NoMTBF site. Stay with me for a moment longer.
Over the years of speaking out on the perils of MTBF, there has been some push back. A few defend using MTBF. Here are three of the most common (maybe not exactly the best, per se) reasons to use MTBF. Continue reading The 3 Best Reasons to Use MTBF
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, industry or whomever to stop using MTBF, you may want to use this simple example to illustrate the ‘value’ of MTBF. Continue reading Illuminating MTBF’s Lack of Information
A Quick MTBF Search Reveals Distressing Results
I was preparing to write this article and wondered how many search hits would appear for MTBF? So, opened Google and did an MTBF search. It is a common if misunderstood, acronym.
Beyond the 5,200,000 Google search results, it was the first page results that got me thinking. Keep in mind that Google often serves up a combination of what it thinks you are seeking and which sites have been useful for others.
Let’s break down what you find when you do an MTBF search. Continue reading MTBF Search Result Sadness
4 Questions to Ask When Confronted with MTBF
MTBF comes up a bit too often. When it does I have found rolling my eyes and arguing against using MTBF is not very effective.
So, what should a knowing reliability professional do instead?
Let’s explore four questions that you can ask that may help others find the value in no longer talking about MTBF. Continue reading 4 Questions to Ask When Confronted with MTBF
Replace After MTTF Time To Avoid Failures – Right?
Received a short question last week. The person writing seems to already know the answer, yet asked:
If we replace an item after a duration equal to the MTTF value, we would avoid failures, right?
Well, no, most likely not, was my response. What is your response? How would you answer this question? Continue reading Replace After MTTF Time To Avoid Failures – Right?
Reliability Goal and Confidence
We establish reliability goals and measure reliability performance.
They are not the same thing. Goals and measures, while related, are not the same nor serve the same purpose. Continue reading The Relationship Between Reliability Goals and Confidence
Yet Another Confused MTBF Definition
Just when I thought we had experienced every possible MTBF definition confusion, here’s another.
This one is courtesy the thread concerning the impact to reliability when adding redundancy to a system. Continue reading Yet Another Confused MTBF Definition
Yet Another Way to Misunderstand MTBF
In a Q&A forum, the response to a question concerning failure rate and repair times for a redundant system demonstrated yet another person confusing MTBF with something it is not.
The responder to the question mentioned the reference to repair time implied the need for MTBF as a metric. Then went on to describe MTBF as the duration of repair time, which should not change given a redundant system over a non-redundant system. Continue reading Another Way to Spot Someone Confusing MTBF
Walking, Playing and Bought a House
Seriously, while out walking, listening to a podcast, and playing Pokemon Go, found an open house to view. A week later our offer was accepted and next week we close.
I would not have been out walking that Sunday afternoon if not out playing Pokemon Go.
Glad there are no dangerous cliffs nearby. Continue reading Bought a House Due to Pokemon Go