All articles listed in reverse chronological order.

Kendall Coefficient of Concordance

Comparisons for agreement

Let’s say we have data that is only rank order from two or more evaluators (people, algorithms, etc.) and we want to determine if the evaluators agree or not.

The agreement here meaning the results from one person or another are in agreement, or they are concordant. This is typically done with this non-parametric method for 3 or more evaluators. For a comparison of two evaluators consider using Cohen’s Kappa or Spearman’s correlation coefficient as they are more appropriate. [Read more…]

by Fred Schenkelberg Leave a Comment

The Learning and Teaching Route to Success

Reliability engineers learn basic tools and techniques most often from others with that knowledge. During our careers, we also continue to learn and often find ourselves teaching. Even when mentoring we find ourselves learning. Being a deliberate and active student and teacher is a great way to remain inquisitive and helpful.

Learning and teaching route to success

Formal education will make you a living; self-education will make you a fortune. [1]

Learning never stops. [Read more…]

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Let the data talk

Plot the data

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. It is a plot of the data that is often all that we need to interpret the data.

[Read more…]

by Fred Schenkelberg Leave a Comment

Three Considerations for Sample Size

Detecting a change or difference is often the aim of an experiment or set of measurements. We want to learn which vendor, process, or design provides a better result.

When we use a sample to estimate a statistic for a population we take the risk that the sample provides values that are not representative of the population. For example, if we use a professional basketball team to sample men’s height. We may conclude that the height of men in the general population is taller than the true population value. [Read more…]

by Fred Schenkelberg 1 Comment

Successful Reliability Engineers Add Value

Value is:

the regard that something is held to deserve; the importance, worth,
or usefulness of something. [1]

As a reliability engineer, we work across the organization to bring a reliable product to market. The value of meeting the customer’s reliability expectations results in customer satisfactions, increased sales, and in some cases premium pricing.

We want a reliable product.

[Read more…]

by Fred Schenkelberg 2 Comments

Mann-Whitney U Test

The U test permits the comparison of two samples to determine if they came from the same population or not. This non-parametric test can use ordinal data, meaning it is in some rank order without containing information about relative distances between ranks. [Read more…]

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Networked and Positive as a Reliability Engineer

Many elements help make a reliability engineer successful.Two such elements are knowing the right people to get the job done and generally being a positive and enjoyable person to be around.

[Read more…]

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1st Annual No MTBF Success Story Challenge

No MTBF Success Story Challenge

]1 Start a conversation over coffee.

Last year I offered a coveted NoMTBF coffee mug to the most traffic generating guest post.

This year, my challenge is for the best success story around your efforts to reduce or eliminate MTBF from use in your organization.

The basic idea is we all have a role to play to clean up the reliability profession. Using clear language is a start. Avoiding the mis-understanding around MTBF is a great start. If we all do something, great or small, toward the goal of eradicating MTBF we all benefit. [Read more…]

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Laplace’s Trend Test

A test to determine if the homogeneous Poisson model (HPP) is applicable given the data from an individual system is subject to the non-homogeneous Poisson model (NHPP).

This is an alternative test to using the Kendall-Mann Reverse Arrangement Test. [Read more…]

by Fred Schenkelberg 1 Comment

Talent and Professionalism as a Reliability Engineer

My dictionary says that talented is “having a natural aptitude or skill for something.”

We learn reliability engineering and those who understand the range of tools and techniques useful for a given situation would be considered talented.

Everything is not solved by running a highly accelerated life test (HALT) or only conducting detailed failure analysis. Knowing when and why to apply a particular tool and using the tool effectively (i.e., when to use a Weibull distribution to model lifetime data and how to use the information to make decisions) are critical. [Read more…]

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Failure Modes and Mechanisms

When something fails, what should we do?

A natural question when something fails is

Why did it fail?

The answer is not always obvious or easy to sort out.

One of my favorite examples was on a circuit board that had a small burn mark where a component exploded off the board. The customer didn’t notice that missing part, our engineering team did that. [Read more…]

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Success as a Reliability Engineer

Whether by design or by accident some of us become reliability engineers. Making a career in reliability engineering relies on your ability to make a difference and to add value. Being successful as a reliability engineer, while creating reliable products, permits continuation and growth as a reliability professional.

[Read more…]

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Why Wait for Field Returns?

In an ideal world, our products and equipment will just work. They would not fail and would not require warranty claims, product returns, or repair.

Unfortunately, we make design mistakes, assembly errors, incur damage, or simply fail. The desired balance for most businesses is the cost of returns will not outweigh the profit of sales.

[Read more…]

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3 Steps NRTL Use for Product Safety

With any product development, there is a risk the features (benefit) come along with inherent dangers (risk). For example, a desktop computer includes the need for electrical power. Done improperly a person exposed to wall current and voltage could be seriously harmed. While unlikely the risk exists. [Read more…]

by Fred Schenkelberg 2 Comments

Reliability Growth Testing

One approach for reliability improvement is to find the weaknesses or faults, then fix them.

This is best done before shipping to the customer.

You may hear this called the Test, Analyze, and Fix Method (TAAF). Or, you may have heard of it called a Reliability Growth Test program (RGT). Either way, the essence is evaluating prototypes to find specific faults. [Read more…]