Which answer mathematically expresses the reliability of an active parallel system in which all component reliabilities are unequal?

Response:

• A.Rs = Ra + Rb + Rc - RaRbRc
• B.Rs = [RaRbRc] / [Ra + Rb + Rc]
• C.Rs = [RaRbRc + RaRb + RbRc + RaRc ] / [Ra + Rb + Rc]
• D.Rs = RaRbRc - (RaRb + RbRc + RaRc) + (Ra + Rb + Rc)

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The mean of the normal logarithms of the repair times is 4.3 hours with a standard deviation of 0.7 hours. What is the maintainability for an allowed repair time of 120 hours?
Response:

• A.0.976
• B.0.757
• C.0.187
• D.0.243

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All of the following are purposes of a production reliability assurance test (PRAT) EXCEPT Response:

• A.Minimize the need for specific process controls
• B.Detect significant shifts between the as-built reliability requirements and the as-designed reliability requirements
• C.Assess actual product reliability against reliability requirements.
• D.Assess performance against reliability requirements.

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For complex electronics systems, the major contributor to repair time is generally:
Response:

• A.Disassembly/reassembly.
• B.Final checkout.
• C.Diagnosis.
• D.Remove/replace.

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Censoring of reliability data indicates which of the following?
I. Biased product data is used.
II. Testing has been failure terminated.
III. The data collection is time limited.
IV. Questionable data collection methods are used.
Response:

• A.I and IV only
• B.II and III only
• C.II and IV only
• D.I and III only

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