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

Issue 23, January 2003

*Hot Topics
*Reliability Basics
*Tool Tips
*Hot News
*Contribute to HotWire

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Hot Topics  
A Look Under the Hood at the Cumulative Damage Model
Past issues of the HotWire and Reliability Edge have presented examples (see Analyzing Step-Stress Data and Analyzing Accelerated Test Data with Time-Varying Test and Use Stress Profiles) that utilize the cumulative damage model. But what is happening behind the scenes? This article will present the cumulative damage model and how it is formulated.

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Reliability Basics  

Comparing Two Data Sets
It is often desirable to be able to compare two sets of reliability or life data in order to determine which of the data sets has a more favorable life distribution. The units from which the data is obtained could either be from two alternate designs, alternate manufacturers or alternate lots or assembly lines. Many methods are available in statistical literature for doing this when the units come from a complete sample, i.e. a sample with no censoring. This process becomes a little more difficult when dealing with data sets that have censoring or when trying to compare two data sets that have different distributions. In general, the problem boils down to that of being able to determine any statistically significant difference between the two samples of potentially censored data from two possibly different populations. This article discusses some of the methods that are applicable to censored data using Weibull++.

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Tool Tips  
  • Can I change the type of Data Entry Spreadsheet I am using in Weibull++ once data has already been entered into it and without having to create a new one?

  • How can I resolve distortion that sometimes appears in charts created with the Chart Wizard?

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Hot News

BlockSim 6 Pre-Release Special - We want to say a special thanks to those who have already taken advantage of the pre-release special. We are still on track to release this software in February 2003. If you have not purchased a license yet, please note that when you order BlockSim 6 before the official product release, you will receive a $500 discount off of the standard price! Special pre-release prices are only $1995 for new users and $495 to upgrade from BlockSim 1.0/1.5. For more information about this ultimate system visualization and analysis tool, please visit


ReliaSoft at RAMS - ReliaSoft will be participating in the 49th Annual Reliability and Maintainability Symposium (RAMS), to be held January 27 - 30, 2003 in Tampa, Florida. ReliaSoft will have a booth in the vendors area where you can get information and demonstrations of ReliaSoft's products and services. We hope to see you there! For detailed information on the symposium, please visit


New Distributor in China - ReliaSoft has recently appointed Sinosome Co. Ltd as a distributor for Mainland China.

* Reliability Training Seminars - Upcoming ReliaSoft public reliability training seminars include:


Master the Subject, Master the Tools training seminar for life data analysis, accelerated life data analysis and system reliability analysis: February 24 - 28, 2003 in Tucson, Arizona. For more information, see


Reliability Black Belt series is designed for advanced instruction pertaining to specific areas of discipline. For more information, see

- Repairable Systems Analysis and BlockSim (Advanced) - March 24 - 26, 2003 in Tucson, Arizona.
- Xfmea - March 27 - 28, 2003 in Tucson, Arizona.
- QALT Boot Camp (Quantitative Accelerated Life Testing Data Analysis) - April 30 - May 2, 2003 in Tucson, Arizona.

Contribute to HotWire
Contributions Welcomed
As always, your feedback and contributions are 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 contributions you may have for Reliability HotWire. If you have a topic or article that you think would be useful to the readers of Reliability HotWire, feel free to contact us.

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