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Kaplan-Meier Reliability: What Could Possibly Go Wrong?

Kaplan-Meier Reliability: What Could Possibly Go Wrong?

SAS, JMP, R-”Survival”, Minitab, ReliaSoft, XLStat, and perhaps other statistics programs offer the Kaplan-Meier nonparametric reliability estimator as a default. Take credit for using nonparametric reliability estimation and avoiding unwarranted assumptions. What could go wrong using the Kaplan-Meier estimator?

  • Cohorts could be non-stationary, random processes! 
  • Failures could be recurrent process counts, not dead-forever! 
  • Lifetime data depends on the censoring process(es); e.g., competing risks!
  • Greenwood’s variance estimator errs! Covariances are missing!
  • Alternative estimators could be more efficient than Kaplan-Meier!

Are you using all the information in data available from population data required by GAAP? If you don’t have lifetime data, use periodic failure counts. This article describes an example where the Kaplan-Meier estimator from grouped lifetime data is less efficient than using periodic failure counts, even though you don’t know which cohort they came from! 

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B10 Life Exponential Distribution

B10 Life Exponential Distribution

This video from the Institute of Quality and Reliability explains how to calculate the B10 life (the time by which 10% of items are expected to fail) for an exponential distribution.

We suggest to view our video on Exponential Distribution for better learning experience. Here is the link to the video:  Remember this Memoryless Exponential Distribution . Your feedback is welcome!

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Leadership Values in Maintenance and Operations

Leadership Values in Maintenance and Operations

The Importance of Having, Setting, and Living Values as a Leader

Leadership is not just about making decisions or achieving results—it’s about setting an example and guiding others toward a common purpose. One of the most powerful ways a leader can do this is by having, setting, and living values that resonate with both themselves and their team. Values are the principles and beliefs that guide actions, shape behaviors, and define the culture of an organization. For leaders in any field, including maintenance and operations, these values become the foundation upon which everything else is built. In the context of Leadership Values in Maintenance and Operations, this foundation is especially critical, as it ensures safety, reliability, and collaboration in high-stakes environments.

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Back to the Basics: Brainstorming for Continuous Improvement

Back to the Basics: Brainstorming for Continuous Improvement

Brainstorming may sound like a casual conversation technique, but when applied properly, it becomes a critical tool for continuous improvement across a range of creative and technical disciplines.
In a structured environment, brainstorming enables organizations to capture a wide range of ideas, perspectives, and solutions — ideas that might never surface in a traditional problem-solving meeting.

Let’s take a step back and revisit the basics of effective brainstorming, especially its role in driving meaningful change.

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What Is RCM? It’s NOT a Maintenance Plan

What Is RCM? It’s NOT a Maintenance Plan

Is Reliability Centered Maintenance (RCM) a maintenance plan?

In this short video, I explain why RCM is NOT a maintenance plan. It’s a process designed to help YOU determine the most effective proactive maintenance tasks and how often to perform them. But that’s not all! In this video I give a quick overview to answer the question: “What is Reliability Centered Maintenance?”

You start by creating a Failure Modes and Effects Analysis (FMEA). Then, you analyze each Failure Mode using the RCM Decision Diagram—one at a time. First, you assess the consequences, then you consider Condition-Based Maintenance or Preventive Maintenance. RCM also helps you formulate solutions for Failure Modes that can’t be predicted or prevented. You can develop solutions like Failure Finding tasks, procedure changes, or additional training.

With RCM, you’ll get the reliability you need, one Failure Mode at a time.

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Leveraging the Supply Chain Operations Reference Model for Inventory Management

Leveraging the Supply Chain Operations Reference Model for Inventory Management

In a previous article, we covered value stream concepts and characterized the value stream in the context of supply chain major sub-processes.  We covered some important key performance indicators related to order fulfillment.

This article will look at work-in-process (WIP) and inventory using the Supply Chain Operations Reference (SCOR) model. 

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Quality Objective 4: Lessons Learned

Every failure is a lesson learned about your strategy. Thomas Edison

In this article, I will discuss how to evaluate an FMEA against the FMEA Quality Objective for Lessons Learned.

By definition, a “lesson” means “something learned by study or experience,” and “learn” means “to gain knowledge or understanding of by study, instruction or experience.”

What are Lessons Learned?

Lessons Learned are specific data from the field (or from manufacturing plant history in the case of Process FMEAs) that documents relevant information about failures, from which knowledge can be gained and used in support of future product programs. [Read more…]

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Quality vs. Reliability

Quality vs. Reliability

Quality: A Snapshot at Time Zero

Quality is a measure of how well a product meets specified requirements and standards at the beginning of its life. It’s a static measure that can be controlled and measured with accuracy. Quality engineers focus on designing and implementing quality control processes, conducting inspections and testing, and identifying and addressing defects or issues.

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Book Review: Accelerated Testing

Book Review: Accelerated Testing

Accelerated Testing: Statistical Models, Test Plans, and Data Analyses by Wayne Nelson

Published by John Wiley & Sons in 1990 this 601 page book started my career in reliability engineering.

I didn’t know it at the time in the early ‘90s, yet my assigned task to create an accelerated test for a new product would spark an interest in cheating time. Wayne’s book helped make that first accelerated test successful.

The Accelerated Testing book is a compendium of different ways to conduct accelerate tests with a focus on the planning the test and analyzing the data. Wayne is a reliability statistician, and as he will tell you, not an engineer. Thus the book tends to focus on the math.

What I enjoy about the book is the math is not the dry academic derivation driven material, it is full of examples and immediately useful formulas. There is just enough explanation to help the math wonks pursue their interest, and enough practical information to allow engineers to develop and conduct meaningful experiments. [Read more…]

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Project Management Ignorance & Breaking Laws

Project Management Ignorance & Breaking Laws

Guest Post by Malcolm Peart (first posted on CERM ® RISK INSIGHTS – reposted here with permission)

Project Management – it’s not covered by a discrete law but when it’s practiced under a contract it’s open to accusations of negligence, just consider the UK’s Hedley Byrne case.  Project Management is seen as a risk mitigation measure and, contractually speaking, this requires a duty of care by its practitioners and/or the legal entity represented.  Ignorance of legal requirements is no excuse for not knowing they exist.

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Minimum Maintenance Strategy by Physics of Failure Analysis

Minimum Maintenance Strategy by Physics of Failure Analysis

 All machines and equipment fail for two reasons—distortion or degradation. Distortion causes parts to suffer such high stress or fatigue that their atomic structures fail. When parts degrade their atomic structure is attacked by environmental elements. Physics of Failure methods lets us analyse equipment for situations that cause their parts’ atomic structures to suffer excessive stress, or to degrade. We can identify the real causes of atomic failure and so institute the fewest maintenance and operational activities to keep equipment at its highest reliability, and the operating plant at its highest availability.

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Are FMEA and RCM Separate Processes?

Are FMEA and RCM Separate Processes?

When you do RCM you also create an FMEA.

In this video, I explain the connection between Reliability Centered Maintenance (RCM) and Failure Modes and Effects Analysis (FMEA). Many people wonder if these are two different processes, but when you perform RCM, the first four steps—defining functions, identifying functional failures, analyzing failure modes, and assessing failure effects—essentially fulfill the requirements of an FMEA. By following the RCM process, you’re already doing the work needed for an FMEA. I break this down and show how they align.

I’m Nancy Regan, and I hope this clears up the confusion! Thank you for watching.

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