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Confidence Bounds in Reliability Growth Planning

You can use the reliability growth planning tool in RGA to determine whether a system’s mean time between failures (MTBF) goal will be met by the end of the test given a set of input parameters such as the initial MTBF, the management strategy and the design margin. One very useful feature of this growth planning tool is the calculation of confidence bounds on the planned MTBF values of each test phase. Once testing begins, the actual demonstrated MTBF of each test phase can be compared with these calculated bounds to determine whether the reliability growth is progressing according to the plan and whether there is a risk trying to achieve the MTBF goal in time. If the demonstrated MTBF of a phase is found to be lower than the calculated confidence bound, that would indicate that the plan is not being followed and the likelihood of achieving the goal MTBF at the end of the test is decreased. If this is the case, testing efforts would need to be adjusted such as changing the management strategy (implementing fixes for more observed failure modes) or ultimately increasing the allocated test time. However, given that planning occurs before testing begins and failures are observed, the question that one can ask is how can RGA calculate confidence bounds in the planning model without the presence of any actual data? This article describes the process of calculating these confidence bounds.


Read the Latest Reliability News

Early Registration Deadline - ARS, Europe

The International Applied Reliability Symposium, Europe will be held in from April 17-19, 2013 in Berlin, Germany. Save €100 by registering early! The advanced registration deadline is February 26, 2013, so don't wait — register now at For more information, including the program matrix, please visit


Call for Presenters - ARS, Asia Pacific

Presenters, time has almost expired to submit your proposals for the 2013 ARS, Asia Pacific, which will be held in Singapore on October 2 - 4, 2013. The presentation proposal deadline is February 11, 2013. If you are interested in learning more about this opportunity and the potential to win an Excellent Presentation Award, please review the detailed instructions posted at


ReliaSoft at RAMS 2013

We will be on location in Orlando, Florida at the Rosen Shingle Creek Resort from January 28 - 31, 2013 to participate in the Annual Reliability & Maintainability Symposium. Our team of reliability experts is looking forward to presenting the following papers, tutorials and panel discussions.

Paper Presentations

Optimizing Maintenance Policies based on Discrete Event Simulation and the OCBA Mechanism by Dingzhou Cao, ReliaSoft, Yu Sun, Siena College, and Huairui Guo, ReliaSoft

Modeling and Analysis for Degradation with an Initiation Time by Huairui Guo and Athanasios Gerokostopoulos, ReliaSoft, Haitao Liao, University of Arizona, and Pengying Niu, ReliaSoft

A Generic Method for Modeling Accelerated Life Testing Data by Haitao Liao, University of Arizona, and Huairui Guo, ReliaSoft

Estimating Component Reliabilities from Incomplete System Failure Data by Huairui Guo, Ferenc Szidarovszky and Pengying Niu, ReliaSoft

Effective Implementation of an Enterprise Supplier Reliability Program with Suppliers by Julio Pulido, ReliaSoft


Understanding Accelerated Life Testing by Pantelis Vassiliou, CEO ReliaSoft Corporation

Determining Right Sample Sizes For Your Test – Theory and Application by Huairui Guo, ReliaSoft, Ed Pohl, University of Arkansas and Athanasios Gerokostopoulos, ReliaSoft

Panel Discussions

Reliability, the Key to a Better Bottom Line Panel Member - Pantelis Vassiliou, CEO ReliaSoft Corporation

We will also be available to demonstrate the capabilities of our complete suite of software tools, including the new Synthesis Platform. So be sure to stop by our booth for a brief visit! For additional information about RAMS, including the final program, please visit

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