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

Issue 1, March 2001

*Hot Topics
*Reliability Basics
*Tool Tips
*Hot News
*From The Edge

Reliability HotWire is a service of ReliaSoft Corporation

To subscribe or update your e-mail preferences, go to


Welcome to the premiere issue of Reliability HotWire, your source of information and tips on how best to improve your reliability practices and get the most out of ReliaSoft’s tools for reliability and life data analysis. Reliability HotWire brings practical hints regarding reliability engineering and life data analysis to the novice and seasoned practitioner alike. In addition, Reliability HotWire will present tips on how to get the best use out of ReliaSoft’s life data analysis software tools, such as Weibull++, ALTA, and BlockSim.

As always, your feedback is appreciated. ReliaSoft is able to provide the most user-friendly reliability software packages and support because we listen to our customers. This applies to our newsletters and publications as well. We welcome any suggestions or comments you may have about Reliability HotWire.

Hot Topics  
Which Analysis Settings Should I Use?

When analyzing reliability data, the analyst is faced with a number of options on how to carry out the analysis. These choices can sometimes seem confusing: Regression or maximum likelihood analysis?  Fisher matrix bounds or likelihood ratio bounds?  Median ranks or Kaplan-Meier estimates?  While there are no hard and fast rules regarding the use of these analysis options, some of these options work better for particular data types than others.

To read more, see 

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

Characterizing Your Product's Reliability

As awareness of product reliability increases, the responsibility for insuring that reliability requirements are met spreads further across engineering organizations. As a result, engineers and managers who have had little experience with life data analysis or applied statistics may find themselves responsible for calculating and reporting on a product's reliability. This section offers background on elementary concepts of reliability and life data analysis that will hopefully prove to be of use to the novice analyst. We will begin our discussion with an overview of how to characterize your product's reliability.

To read more, see 

Tool Tips  

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

  • Why doesn't the calculated MLE line track the data points on my probability plot in Weibull++?

  • I have installed Weibull++ or ALTA with no problems, but when I attempt to open a Folio, I get an error message.

  • In BlockSim, how can I simultaneously change the values of more than one block in the RBD?

  • Can I share plots from ReliaSoft applications with colleagues who do not have the applications installed on their computers?

To read more, see

Hot News

*Weibull++ Version 6 Released - The latest and greatest version of Weibull++, the premiere reliability and life data analysis package, is now available. You can download a free evaluation copy from This version has all of the features and usability you have come to expect from ReliaSoft products, with a host of great new features. These include: the generalized-gamma distribution, likelihood ratio bounds, competing failure modes, warranty analysis, ANOVA, a redesigned Report Work Center, and a whole lot more! Weibull++ 5 users can upgrade to Version 6 for $295. For details on the updated version of Weibull++, see

*Reliability Books Online  - The latest version of ReliaSoft's Life Data Analysis textbook is now available online at  in a searchable HTML format. Check it out at

*ReliaSoft at RAMS - Once again, the ReliaSoft team made a big splash at the annual Reliability and Maintainability Symposium, which was held in Philadelphia from January 22 - 25. ReliaSoft personnel presented papers on the following topics:

  • Determination & Interpretation of Activation Energy Using Accelerated-Test Data (Paper)

  • System Reliability Analysis: The Advantages of Using Analytic Methods to Analyze Non-Repairable Systems (Paper)

  • Warranty Calculations for Missiles with Only Current-Status Data, Using Bayesian Methods (Paper)

  • Reliability Leadership (Paper)

  • Understanding Accelerated Life-Testing Analysis (Tutorial)

Details and copies of these and other papers presented by ReliaSoft personnel at previous RAMS gatherings can be found at

*Next Seminar in Tucson, April 2-6 - The next ReliaSoft "Master the Subject, Master the Tools" seminar will be held in Tucson from April 2-6, 2001 at the Sheraton Tucson Hotel and Suites. 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

*ReliaSoft's sales group has moved to Tucson - We are happy to announce that our Corporate Sales group (formerly in Minneapolis, MN) has moved to our recently expanded Corporate R and D facilities in Tucson, AZ, giving us a closer integration between sales and product development staff. We expect this integration to translate into even better products and services. During this transition, the phone and fax numbers used in Minneapolis have been changed. As of February 9, 2001 please use the following numbers:

  • Toll Free Sales Number: 1-888-886-0410 (or via a toll call from international locations 1-520-886-0410)

  • Fax: 1-520-886-0399

*Reliability consulting now available through ReliaSoft Professional Services --- ReliaSoft Professional Services now offers expert consulting help. For more information see

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 current edition include:

  • Life Data Classifications - Knowing how to distinguish between different types of life data is vital to being able to properly analyze such data. For a graphical example of the different types of life data and how they differ, see

  • The Limitations of Using MTTF as a Reliability Specification - The mean life or MTTF (mean time to failure) is a popular measure of the life or reliability of a product. Its seeming simplicity and ease of understanding have made this a popular reliability metric, particularly for engineers and managers with little or no background in reliability and statistics. However, the MTTF metric may not be giving you the information necessary for making an informed decision about a product's reliability. To read more about the limitations of the MTTF as a reliability metric and suitable alternatives, see

  • Using Reliability Importance Measures - Reliability importance is a measure of the contribution of an individual component to the overall reliability of a system. The reliability importance measurements can then be used to determine the allocation of resources for system reliability improvement. This information is useful in minimizing the development costs of increased reliability. For more information on the formulation and use of reliability importance measures, see

Look for these articles in the next edition:

  • Predicting Warranty Returns
  • A Simple Demonstration of Accelerated Life Testing Analysis
  • Exploring Reliability Analysis Using Simulation
  • A High Value of Beta is Not Necessarily a Cause for Concern
ReliaSoft Logo

Copyright © 2001 ReliaSoft Corporation,