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IPRA was developed at the Institute
for Reliability and Risk Analysis, and forms part of a suite of
programs designed to work in the Microsoft Windows environment.
OVERVIEW
The program is concerned with the use of expert opinion, especially methods
of combining expert opinion from multiple experts. The setting is reliability
testing of components, where it is assumed that times to failure are
Weibull distributed. This means that a large range of scenarios can be
considered, such as components that wear or improve with age, or components
that are unaffected by usage.
A large part of the program is concerned with eliciting opinion from
experts in the field, by asking a sequence of easy questions about the
characteristics of the item on test. The process is highly interactive,
especially in the entering of distributions, where extensive use is made of
drag-and-drop facilities. In addition to the opinions of two experts, a
decision maker is required to make judgements about how the two experts
interact - whether they tend to agree or disagree, and whether they are
generally optimistic or pessimistic.
Once opinions have been elicited, data from reliability testing may be
entered, and based on this data, analysis performed. This analysis
calculates the prior and posterior distributions of the parameters of the
life length model, plus the reliability of components at ages specified by
the user. The distributions can be viewed using either 2- or 3-dimensional
formats.
The main aspects of the software are highlighted below:
DATA INPUT
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The software has an input screen, for entering
data from reliability testing. There is also a highly interactive procedure
for eliciting expert opinion.
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ANALYSIS
Once expert opinion and reliability data has been entered, there are a
number of analysis options available to the user.
RESULTS
Results can be displayed using a variety of two and three-dimensional plots.
2-D plot of median showing prior and posterior
OTHER FEATURES
The program has all the usual features of a Windows-based program,
including full file management facilities and the facility to print the
results either in tabular or graphical form.
REFERENCE
Singpurwalla N. D. (1988). 'An Interactive PC-Based Procedure for
Reliability Assessment Incorporating Expert Opinion and Survival Data.' Journal
of the American Statistical Association, 83, 43-51.
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