The Role of Statistics in Reliability Engineering

This Isn’t Your High School Statistics Course

What does the word statistics bring to mind when you hear it? Horrible high school classes that you sat through wondering why do I need this stuff? Complex math problems what were almost impossible to figure out? Or is it nonsense that is only used in political polls?

Statistics are used in every aspect of Reliability Engineering. So if you don’t have a good relationship with statistics, I highly recommend that you are starting investing time in building your knowledge in statistics. [Read more…]

by Fred Schenkelberg 2 Comments

The Sum of Squares Concept

The data analysis course professor tended to focus on the practical application of statistics.

Avoiding statistical theory was fine with me. Learning statistics for me was on how to solve problems, optimize designs, and understanding data.

Then one lecture started with the question, “Why do we sum squares regression analysis, ANOVA calculations, and with other statistical methods?” He paused waiting for one us to answer.

We didn’t. I feared the upcoming lecture would include arcane derivations and burdensome theoretical annotations. It didn’t. [Read more…]

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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. [Read more…]

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Improve Decision Making with Statistics

We make decisions all the time. Often our decision making is with little more than a gut feeling.

When faced with a major decision we often look data to help us decide. Is the product reliable enough as designed? Which field returns indicate we should stop production?

Some decision may help us earn or lose thousands if not millions of dollars.

Deciding to delay a product launch by six months means we have no revenue for the duration. The delay may also permit us to address a design flaw that would cause half the products to fail within a few months.

The later may cause loss of market share, erosion of brand loyalty, not to mention the cost of warranty claims. [Read more…]

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Show me the Data

Early in my career, I worked for an unreasonable person.

He wanted us, his engineering staff, to show him the data. He wanted us to gather, monitor, analyze and display data regularly. Anytime we needed approval, funding, or resources he wanted to see the data. [Read more…]

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How to Encourage the Use of Statistics

If nothing was uncertain we would not need statistics.

Since nearly everything varies in some fashion, we need a way to describe and work with that variability.

We already know this and we know about statistics as being the right set of tools. Yet we hesitate, avoid, and refuse to pick up the appropriate tool. [Read more…]

by Fred Schenkelberg 2 Comments

Probability and Reliability Goals

Roll the dice.

It is about that simple if any one product will survive to a specific time. Every product has a chance, not a guarantee. The time to failure for each product is a function of the use, stresses, assembly, latent defects or imperfections, and many other variables.

The result is generally unknown. And, we often establish a reliability goal that includes the probability of success. Keep in mind that a probability is only meaningful when defined over a specific duration.

[Read more…]

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The Meaning of a Failure

Every failure provides information. It provides time to failure, stress strength relationship, process stability and design margin types of information. In every case. Even failures directly related to human error.

A hardware intermittent failure observed by a firmware engineer should not be dismissed. Rather recorded, explored and examined.

A single intermittent failure, or glitch, may indicate nothing other than just a totally random glitch, or a design error that degrades over time causing 50% of units to fail in first three months.

[Read more…]

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Reliability is Not Just Statistics

In a common definition used by engineers reliability is a probability of success. It is the chance of an item operating as expected over some duration in a given environment. In this case, we have probability as part of the definition of reliability.

Reliability in common use definition includes trustworthiness, dependability and similar definitions. It’s more than how many times your friends help you move to a new apartment, it’s a feeling or sense we have concerning our ability to count on our friends for the help.

[Read more…]

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Sample size

I recently received a question concerning what sample size to use when assessing call center calls. Not a lot of information in the request, so my answer was rather general. And, thought it might provide some insight to others facing sample size questions of their own. [Read more…]

by Richard Coronado 1 Comment

Hypothesis Testing

This week in our CRE Test Prep class/webinar we covered the Advance Statistics section of the CRE Primer, and I felt great that we stayed an hour more going over these though topics.

One of the topics was Hypothesis Testing.

Let me share some of the questions that arose during that section. [Read more…]

by Richard Coronado 1 Comment

Confidence Limits

Last week during our CRE Test Prep class, we were covering the Basic Statistics section in the CRE Primer and had several questions regarding Confidence Limits for Reliability.

All of them were fair questions, and when students are asking these types of questions, the class gets better… [Read more…]

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5 Reliability Training Options

Just answered a question on where to find reliability engineering training on basics and statistics. There are plenty of options and below I’m listing just where to find the many, many options available to you. [Read more…]

by Fred Schenkelberg 5 Comments

Statistical Terms about Variation

“Statistics is the language of variation.” I’m sure that is a quote by someone, not me, though. It is true. Statistics is all about variation. In this post let’s explore some of the ways statisticians talk about data and specifically the amount of dispersion in the data. [Read more…]

by Fred Schenkelberg 1 Comment

Role of Reliability Statistics

Generally, I do not talk about statistics before 10am – it’s not polite.

As a reliability professional, statistics is a central feature of the value I bring to the team. And, not just the reliability statistics, all stats. It continues to amaze me how many engineers, scientists, and professionals tend to avoid statistics. [Read more…]