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Unformatted text preview: Therefore: FR(N) = 6/148,000 = 0.0000405 failures/hour MTBF = 1/FR(N) = 24,691 hours Problem 2: Converting the units of FR(N) to months: FR( N ) = 0.0000405 * 24 hours/day * 30 days/month = 0.029 failures/month FR(N) for the 300 units: FR( N ) = 0.029 failures/month * 300 units = 8.75 failures/month MTBF for the mainframe: MTBF = 1/FR( N ) = 1/8.75 = 0.11 month = 0.11 * 30 = 3.4 days Calculation for MTBF assumes that failure of any one chip brings down entire system. Problem 3: [0.95 0.92(1 0.95)] * [0.98] * [0.90 0.90(1 0.90)] R = ++= 0.996 * 0.98 * 0.99 = 96.6% Problem 4: 3 Number of Breakdowns Daily Frequency Probability 3 0.3 1 2 0.2 2 2 0.2 3 3 0.3 Expected number of breakdowns = (0)(0.3) + (1)(0.2) + (2)(0.2) + (3)(0.3) = 0 + 0.2 + 0.4 + 0.9 = 1.5 breakdowns/day Expected breakdown cost = Expected number of breakdowns * Cost per breakdown = 1.5 * $10 = $15/day 4...
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 Spring '09
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 Maintenance and Reliability

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