Reliability Information Analysis Center Forums Weibull Analysis Results
 Register FAQ Members List Search Today's Posts Mark Forums Read

#1
11-04-2002, 06:20 AM
 Guest Senior Member Join Date: May 2007 Posts: 968
Weibull Analysis Results

I am analyzing field failure data of an electronic system. When performing a Weibull analysis, I find a beta of 0.952 with 19 samples. The source of information is only accurate to the day (i.e., I only know what date a failure occurred, not exact time), so I expected some error from this. Given the age of the equipment being analyzed, it would be expected to be operating within it's useful life. How far from 1.00 does the beta need to be before I would be wrong in using an exponential distribution? How much error can I expect due to the time reporting limitations of my data source?
#2
11-05-2002, 10:39 AM
 RIAC Staff Member Administrator Join Date: May 2007 Posts: 664
Weibull Analysis

To answer this two-part query we revisit the original problem. First, Mr. Rowland is using a well-known Weibull property [1,2,3,4,5]: if its shape parameter (Beta) is unit, Weibull reduces to an Exponential with mean, the scale parameter (Alpha). But Mr. Rowland is working with a sample, not with the population. Hence, there is a sampling error in his point estimation of the shape parameter Beta, which is a function of two factors: the sample size and other Weibull parameters (e.g. mean, variance, and scale).

Therefore, without having access to Mr. Rowland's sample there is no way to say whether 0.952 is good enough to assume Beta is unit (and Exponentiality of the data) or whether it is not.
#3
11-05-2002, 11:45 AM
 Guest Senior Member Join Date: May 2007 Posts: 968
Weibull Beta Confidence

All good points made. I agree. Now, just like you can construct confidence bounds around the Weibull characteristic life, you can also construct confidence bounds around the shape factor, Beta. That should help you to see how far the spread is above and below 1.0.
#4
12-08-2011, 04:01 AM
 denielnill Junior Member Join Date: Oct 2011 Posts: 3
Weibull Analysis

With rising production pressures it is critical to predict failures and prevent breakdowns. A systematic FMEA analysis, breakdown analysis and Weibull analysis can help avoid failures.
#5
02-14-2012, 10:10 AM
 dvaidr Guest Posts: n/a

I notice that you are using Weibull for fielded items. Make sure you use MLE as opposed to straightforward Weibull, which assumes a perfect repair.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home RIAC Topics     Component Reliability         Electrical Component Reliability         Non-Electrical Component Reliability     Software Reliability     Maintainability/Supportability     Quality     Interoperability     Reliability Models     Data Analysis and Testing     Handbooks and Standards RIAC Products and Services     217Plus     Training Courses General Category     Main Forum     General RIAC WARP Forum     General Comments     Gaps in PoF Model Research     Comments on a Specific Model

All times are GMT -4. The time now is 08:57 AM.