Your Reliability Engineering Professional Development Site
A listing in reverse chronological order of articles by:
How to distinguish a renewal process from a “generalized” renewal process? Compare observed monthly returns vs. actuarial returns forecasts using actuarial return rate estimates of TTFF and TBF (Time To First Failure and Time Between Failures). A geophysicist masquerading as an Apple reliability engineer said, “It’s too hard to figure out the probability that a return came from a computer made in an earlier year.” It’s harder if returns could be second, third, or???
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Institute of Quality and Reliability is happy to release this second video on ANOVA! Viewers need to watch our video ANOVA Part-1 before watching this video. In this video, Hemant Urdhwareshe explains One-way ANOVA calculations using Sum of Squares on Excel. Hemant is a Fellow of ASQ and is certified by ASQ as Six Sigma Master Black Belt, CQE, CRE and CMQ/OE.
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Institute of Quality and Reliability (IQR) is happy to release this first video on Analysis of Variance (ANOVA). In this video, Hemant Urdhwareshe, Director of IQR and Fellow of ASQ, explains basic concepts of ANOVA and F-test of equal variances.
[Read more…]“I cannot teach anybody anything, I can only make them think.” — Socrates
Effective teaching results in the target knowledge and skills being conveyed to the student, with each student having a working knowledge of the content, and able to apply the subject matter successfully. You have successfully taught a subject when students understand the material and have attained the ability to apply the skills for the subject being taught. [Read more…]
“Quality is not act. It is a habit.” – Aristotle
This month will begin a new series of articles on the quality of FMEAs, part of the Inside FMEAs series. The series will provide insights and application tips for evaluating how well an FMEA meets quality objectives. The intent is to create FMEAs that add value by accomplishing the objectives for FMEA, not filling out a form.
We’ll begin with definitions from the Oxford English dictionary. “Quality” is defined as “the standard of something as measured against other things of a similar kind; the degree of excellence of something.” “Objective” is “a thing aimed at or sought; a goal.”
Building from the above definitions, FMEA quality objectives are specific goals or aims that measure the degree of excellence of an FMEA. [Read more…]
Dear friends, we are happy to release this seventh video in our series on hypothesis testing. In this video, Hemant Urdhwareshe explains the applicability of proportion tests, procedure to perform these tests and interpretation of results. The concept is explained with application examples. Do let us know your feedback and subscribe if you like!
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For engineering, quality and manufacturing professionals, the accuracy and precision of measurement systems are essential. Gage Repeatability and Reproducibility (Gage R&R) studies provide a formal method for evaluating measurement system variation. And when the results of a study indicate that the gage is unacceptable, it’s a signal that something needs to change. But how should you approach solving the problem? This article provides a detailed guide to systematically troubleshoot and improve your measurement system when your Gage R&R results fall short of expectations. [Read more…]
Dear friends, we are happy to released this sixth video in our series on hypothesis testing! In tis video Hemant Urdhwareshe has explained procedure to perform chi-square test in case of contingency tables. Our objective is to compare different groups to assess whether these are independent or related.
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“It is the policy of my Administration to respond to the coronavirus disease 2019 (COVID-19) pandemic through effective approaches guided by the best available science and data” [Biden Executive order, 2021]. That epidemic inspired the simultaneous nonparametric estimation of survival functions from case to recovery and case to death, without lifetime data (figure 1)!
Why not do the same for multiple-failure-mode data? This article shows nonparametric, multiple-failure-mode, maximum likelihood reliability estimation in a spreadsheet. Data are system first-failure times and the corresponding failure modes that caused the first system failures (table 1). However those data are dependent. I will explain the likelihood function, lnL, and how to find the maximum likelihood reliability estimates for all failure modes simultaneously.
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Dear friends, we are happy to released this fifth video in our series on Hypothesis Testing! In this video, Hemant Urdhwareshe explains the applicability of Chi-square test of one variance with an illustration! Hemant is Fellow of ASQ and is one of the few Certified Six Sigma Master Black Belts from ASQ having six certifications from ASQ.
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The term Measurement Systems Analysis refers to a collection of experimental and statistical methods designed to evaluate the error introduced by a measurement system and the resulting usefulness of that system for a particular application.
Measurement systems range from the simplest of gages like steel rulers to the most complex, multi-sensor measurement systems. Yet regardless of their sophistication, all gages are flawed and fail to deliver a perfectly accurate result to their users. This idea is best expressed by an equation fundamental to measurement science,
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Dear friends, we are happy to release our fourth video in our series on Hypothesis Testing! In this video, Hemant Urdhwareshe explains the application of Student’s t-test for paired t-test using tables of t-distribution and using Microsoft Excel Add-ins. The concept is illustrated with an application example of comparing assessment of answer papers by two professors!
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When a system fails for the first failure in one mode at time t, this data is right censored data for other failure modes! How to estimate reliability functions for all failure modes from first failure data?
Google AI says, “’Competing risks’ refers to a statistical scenario where a subject can experience failure from multiple possible causes, but once one failure occurs, it prevents the observation of any other potential failures, essentially creating “multiple failure modes” that compete with each other to be the first event observed; this means analyzing the probability of a specific failure type needs to account for the possibility of other competing failures happening first.” “Use appropriate statistical methods: Employ statistical models specifically designed for competing risks analysis…”
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Dear friends, we are happy to release our third video in our series on Hypothesis Testing! In this video, Hemant Urdhwareshe explains the application of Student’s t-test for comparison of two independent samples using tables of t-distribution and also using Microsoft Excel Add-ins. The concept is illustrated with an application example of comparing tire life of two makes.
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Our work as quality and reliability engineers, or as countless other technical positions across every industry, relies heavily on the instrumentation we use. Torque meters, tensile testers, micrometers, spectrometers and coordinate measuring machines provide critical data about the variation within the processes we design and maintain.
But these tools execute measurement processes which, like all processes, introduce variation into the results they generate. This fact – that every gage contributes variation to the values it reports – is the basis for Measurement Systems Analysis (MSA), a collection of statistical tools and approaches designed to isolate and quantify sources of measurement error.