Forum Questions and Answers
Topic: PRISM Questions and Answers
Topic Posted by: SRC ( )
Organization: SRC
Date Posted: Wed Jan 12 8:33:33 US/Eastern 2000
Topic Description: Welcome to the PRISM forum! Please feel free to post your questions and comments about the PRISM assessment software here.

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Original Message:
Posted by: Leroy Meyers ( )
Organization:DRS Communications
Date posted: Tue Nov 13 15:24:50 US/Eastern 2001
Subject: Making Sense of Prism
I just completed my first Prism reliability prediction. I used the same piece of equipment for which I used MIL-HDBK-217F previously. I was very interested in comparing the results, so I used a 100% duty cycle in Prism so that calendar hours would equal operating hours. Using 217, the failure rate of the equipment is 83 failures per million hours. I inserted all the same parts into Prism, and came up with a failure rate of 6. I'm thinking that 6 is a very low number; will anyone believe it? But then I realized that I forgot to put the software failure rate into Prism. That's understandable, because software is something that I never considered in a prediction before. So I entered in the software parameters. That alone gave me a failure rate of 17,071!! Now I'm at the other extreme - this failure rate is way too high, I can't use this! Has anyone else gone through this? How can I make sense of this? If you want to know the details of what I entered into Prism, you can contact me directly at
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