Field data for 20 mechanical suspension systems showed 3 failure during the 12 month warranty period.
When failure occurred they were repair within 2 days and the system returned to operation. If the time of failure for the failed system were 4.4 moths, 6.3 months, and 10.7 months after placement in the field, what is the 90% lower confidence estimate on MTBF?
Response:

• A.33.7 months
• B.43.5 months
• C.4.1 months
• D.35.9 months

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A certain light switch fails with a failure rate of 10 -4 . If the switch is used 20 times per week, what is the probability of the switch failing by the end of 3-year period?
Response:

• A.7.32 × 10 -1
• B.3.12 × 10 -1
• C.7.32 × 10 -5
• D.2.68 × 10 -1

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FMECA is:
Response:

• A.A formal technique for review of failure potentials during design.
• B.A technique useful for space-government project.
• C.A technique to assure that design performance guidelines are fulfilled.
• D.A professional engineering organization.

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Failure occur on a system at 75, 79, 83, 85 hours. Assuming normality, one sided and unbiased the lower tolerance limit for 95% reliability with 90% confidence for this sample is:
Response:

• A.100 hours.
• B.96 hours.
• C.60 hours.
• D.63 hours.

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The primary aim of sequential-life testing is to determine
Response:

• A.Whether the stress-level variation is significant.
• B.The mean time between failures (MTBF).
• C.The probability density function of failures.
• D.Whether a lot meets the reliability goal.

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