Reliability HotWire: eMagazine for the Reliability Professional
In this issue:

Issue 9, November 2001

*Hot Topics
*Reliability Basics
*Tool Tips
*Hot News
*From The Edge
*Put Yourself on the Hot Seat

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Hot Topics  
Determining the Connection Between Test and Field Reliability
One of the most difficult activities for a reliability engineer is making a quantifiable connection between reliability results from in-house testing and the reliability experienced by items in the field. Often, tests will be performed on products in development in order to make an estimate of the reliability in the field. The results of these tests, however, may not match the actual field performance once the product has been released. In this article, we look at a way of using the proportional hazards model to help quantify an acceleration factor that can link lab and field reliability performance.

To read more, see 

Reliability Basics  
The purpose of this section is to offer background and advice to the novice reliability engineer.

Maximum Likelihood Estimation
In last month's Reliability Basics, we looked at the probability plotting method of parameter estimation. Maximum likelihood estimation (MLE) is another popular method for estimating distribution parameters for reliability and life data. This is considered to be one of the most robust parameter estimation techniques. In this article, we take a basic look at the methodology behind this powerful estimation technique.

To read more, see 

Tool Tips  

The Tool Tips section addresses helpful hints and frequently asked questions about ReliaSoft software products.

  • Is there a way that I can display probability scales on the probability plots in Weibull++?

  • Does BlockSim handle k-out-of-n parallel redundancy configurations?

To read more, see

Hot News
* ALTA 6 is Making an Impact - With the release of ALTA 6 and ALTA 6 PRO only three months ago, accelerated testing studies that were once nearly impossible can now be completed with a few clicks of a button. For real-life accelerated testing analysis case studies, including those submitted by ReliaSoft's customers, see If you have an ALTA 6 PRO success story you would like to share, see for submission information. For testimonials from customers who used ALTA to help their organizations, see

*Next Seminar in Tucson, December 10-14 - ReliaSoft's next "Master the Subject, Master the Tools" seminar will be held in Tucson, Arizona from December 10-14, 2001. Topics for this five-day seminar include life data analysis, accelerated life testing, and system reliability, maintainability and availability. For more information on course content and how to register, see 

*Integrate Weibull++ Engines in Your Own Application  - Developers can now use the Weibull++ 6 DE (Developer Edition) software to integrate Weibull++ and/or Weibull++ calculation and plotting engines into custom designed software applications. Now, you can create your own applications with functionality similar to Weibull++, automate data analysis in applications like Excel or Access and/or create applications that link to corporate data centers and perform automated analyses. Weibull++ 6 DE provides access to ReliaSoft’s Weibull++ engines via the use of the RSW6API.OCX and access to the complete Weibull++ interface through the RSW6I.DLL library. For more information, see
  *ReliaSoft to Co-sponsor the 39th Annual Reliability Engineering and Management Institute  - Along with Boeing, Dell, Ford, General Electric, Hewlett-Packard, IBM, Honeywell, Raytheon (to name a few), ReliaSoft will once again be co-sponsoring the Annual Reliability and Maintainability Management Institute. The institute will be held November 12-15 in Tucson, Arizona. If you will be attending the institute, we would love to meet you at the ReliaSoft corporate headquarters, conveniently located nearby. Call 520.886.0410 if you would like to arrange a meeting to discuss your reliability needs. Also, be sure to attend the overview of ReliaSoft's reliability engineering software tools, given by ReliaSoft's President and CEO Pantelis Vassiliou on Tuesday, November 13.
From the Edge  
Every quarter, ReliaSoft publishes Reliability Edge, a printed journal that includes articles and information related to the field of reliability engineering. Articles of interest in the upcoming edition, scheduled for a December 2001 release:
  • Limitations of the Exponential Distribution for Reliability Analysis - The exponential distribution is widely taught and used as a lifetime distribution due to its relative mathematical simplicity. However, assumptions implicit in the use of this distribution may not be applicable to the data being analyzed. Take a look at this article to learn when and how to use the exponential distribution - and when to avoid it.
  • Introduction to Accelerated Testing Types - As product development cycles become shorter and warranty times become longer, the popularity of accelerated testing becomes more widespread. However, it is easy to get confused by capability claims for certain types of accelerated testing. This article takes a look at different types of accelerated tests, and what one can reasonably expect to achieve with them.

Reliability Edge is a published quarterly. To obtain a FREE subscription, see

Put Yourself on the Hot Seat
Success Stories Wanted
Periodically, Reliability HotWire runs a feature called "On the Hot Seat," where reliability professionals share their experiences with ReliaSoft software tools and how they have helped solve problems on their day-to-day job assignments. We are always on the lookout for more success stories from those reliability professionals willing to put themselves "on the hot seat."
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