Transcript Problem 13-20 Yacht Construction Project

Problem 13-20
Yacht Construction Project
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Expected completion time is 21 months
Project variance is 4
Standard deviation is 2 (square root of 4)
Total project completion time follows a
normal probability distribution, so can be
graphed as an area under a bell-shaped
curve
Jan White, BUS340
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A. What is the probability that the project
will be completed in 17 months or less?
• z = (due date - expected date) divided by the
standard deviation
• z = (17-21)/4 = -4/2 = -2 (two standard
deviations to the left of the mean)
• z = 1-.97725(from Appendix A) = 0.0227,
or 2.27% probability
Jan White, BUS340
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B. What is the probability that the project will
be completed in 20 months or less?
• z = (20 - 21)/2
• z = -1/2 (one-half of the deviation to the left
of the mean)
• z = 1 - .69146 = 0.3085, or 30.85%
probability
Jan White, BUS340
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C. What is the probability that the project will
be completed in 23 months or less?
• z = (23 - 21)/2
• z = 2/2 (one standard deviation to the right
of the mean)
• z = 0.84134, or 84.13% probability
Jan White, BUS340
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D. What is the probability that the project
will be completed in 25 months or less?
• z = (25-21)/2
• z = 4/2 (two standard deviations to the right
of the mean)
• z = 0.97725, or 97.73% probability
Jan White, BUS340
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