I forwarded the note below to QCI for comment and asked if they have an errata available. They do.
The QCI errata is posted on [the] website.
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A friend of mine is studying for the CRE exam and while working an example in the CRE Primer from the Quality Council of Indiana – had the following question.
I’m hoping you can help me out. I am preparing for the March CRE exam and have encountered a problem trying to understand one of the example in the Quality Council of Indiana’s CRE Primer. It’s in Section VIII, Maintainability and Availability and has to do with estimating an MTTF Improvement Factor (Example 8.21 on page VIII-62). I think it may be a notation issue and possibly a typo or two. In the equation for MTTF-PM, they have a Lambda-PM and I cannot determine how they came up with Lambda-PM. I also can’t find a reference for this problem. If I assume Lambda-PM is 1/90 hours (is that the correct thing to do?) and do the math, I obtain a numerator in the final answer for MTTF-PM = 135, rather than the 135.14 the Primer indicates.As if that isn’t enough, I can’t get the value the Primer shows in the denominator either. I get 0.3522 rather than the 0.3995 shown in the primer.
So, for those without the primer handy, – here’s the example (scanned)
So, what is Lambda-pm and are the calculations correct in the example?
I don’t think so – yet cannot explain this for sure – and rather than maybe lead you down the wrong path, I’m looking for some confirmation that example is right or wrong, and why?
And, in a larger sense, if you know of typo’s in the CRE Primer – maybe this site could be a good spot to collect those and create a CRE Primer addendum/corrections listing. Let’s talk about what we know that can improve the CRE Primer and help those preparing for the CRE exam.