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

Issue 57, November 2005

*Hot Topics
*Reliability Basics
*Tool Tips
*Latest Software Updates
*Hot News
*Contribute to HotWire

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Hot Topics

Applications of Non-Parametric Recurrent Event Data Analysis in Reliability Engineering

Recurrent Events Data Analysis, also called Recurrent Event Data Analysis (RDA), can be used in various applied fields such as reliability, medicine, social sciences, economics, business and criminology. The non-parametric approach for modeling Recurrent Events Data Analysis is an easy methodology.


The non-parametric recurrent event data analysis method provides a nonparametric graphical estimate of the mean cumulative number or cost of recurrence per unit versus age. In the reliability field, the non-parametric recurrent event data analysis has many applications. Some of the applications are:

  • Evaluating whether the population repair (or cost) rate increases or decreases with age (this is useful for product retirement and  burn-in decisions).

  • Estimating the average number or cost of repairs per unit on warranty or over the design life of the product.

  • Comparing two or more sets of data obtained from different designs, production periods, maintenance policies, environments, operating conditions, etc.

  • Predicting future numbers and costs of repairs.

  • Revealing unexpected information and insights.

To read more, see 

Reliability Basics

Introduction to Non-Parametric recurrent event data Analysis

In life data analysis (LDA), it is assumed that events (failures) are independent and identically distributed (iid). However, there are many cases where events are dependent and not identically distributed (such as repairable system data) or where the analyst is interested in modeling the number of occurrences of events over time rather than the length of time prior to the first event, as in LDA.


Weibull++ provides two approaches to analyze such data:

   The non-parametric approach:

The focus of this article, this approach is based on the well-known Mean Cumulative Function (MCF). Weibull++'s Non-Parametric RDA module for this type of analysis builds upon the work of Dr. Wayne Nelson, who has written extensively on the calculation and applications of MCF [1].

  The parametric approach:

Weibull++'s Parametric RDA module for this type of analysis is based on the General Renewal Process (GRP) model, which is particularly useful in understanding the effects of the repairs on the age of a system. The parametric approach will be discussed in future issues.

To read more, see 

Tool Tips
  • Which degradation model should be used in Weibull++ 7s Degradation Analysis Folio?

  • How can cells, Data Sheets and formulas be referred to quickly in Weibull++ 7?

To read more, see 

Latest Software Updates
New service releases are now available for Weibull++ (SR 7.0.4), RGA (SR 6.0.5), Xfmea (SR 3.0.4), RCM++ (SR 3.0.4) and RENO (SR 1.0.6). To determine the compile revision of the application on your computer, select About from the Help menu. More Software Downloads...


Application Date Created Version
Weibull++ 7    
Weibull++ 7 11/1/05 7.0.4
Weibull++ 7 Update N/A SR 7.0.4
RGA 10/27/05 6.0.5
RGA Update N/A SR 6.0.5
Xfmea 10/20/05 3.0.4
Xfmea Update N/A SR 3.0.4
RCM++ 10/20/05 3.0.4
RCM++ Update N/A SR 3.0.4
RENO 11/10/05 1.0.6
RENO Update N/A SR 1.0.6
Hot News
* NEW - Weibull++ 7 - The new Weibull++ 7 ( has been flying off the shelves. We'd like to thank you very much for showing such enthusiastic support by investing in this new release. We have also restocked our supplies of the technical reference guides, so we are once again filling orders the same day they are received. Single user licenses and upgrades can be purchased locally from our online store (USA/Canada) or directly from an international supplier near you. Here is the link to our Worldwide Directory:
* Applied Reliability Symposium, Orlando 2006 - Please mark your calendars and begin thinking about attending the 2006 Applied Reliability Symposium ( next June in Orlando, FL.  The symposium has been booked for the Sheraton World Resort which is walking distance from Sea World and 5 minutes away from Walt Disney World and Universal Studios. Registrations are currently being accepted at
* 52nd Annual Reliability & Maintainability Symposium (RAMS) - ReliaSoft Corporation will be a participant at RAMS again this winter. The event is scheduled for January 23-26, 2006 at the Marriott Hotel in Newport Beach, California. Topics related to Reliability, Maintainability, Quality, Risk Management and Safety will be addressed as engineers are exposed to state-of-the-art methods for achieving their R&M objectives. For more information and an Advanced Program, see
* Holiday Hours - Please note that our Corporate Headquarters in the USA will be closed on Nov. 24th & 25th, 2005.
Public Training Event Calendar
November 2004
November 21 - 25, 2005: MSMT Foundations in Melbourne, Australia
December 2005
December 7 - 9, 2005: RS 521 QALT Boot Camp in Tucson, Arizona
December 7 - 9, 2005: RS 511 Reliability Growth Analysis and RGA in Tucson, Arizona
February 2006
February 27 - March 3, 2006: MSMT Foundations 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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