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.

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.

Tool Tips

• 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?

Hot News
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 http://www.ReliaSoft.com/newsletter/index.htm.

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."