Question 1006317: The clean-up crew of a medium-sized firm has an average clean-up time of 72.0 total hours with a variance of 64 hours squared. The clean-up times are bell-shaped. (a) What proportion of the time will it take the clean-up crew 56 or more hours for cleaning the plant? (b) Ninety-five percent of the time the total clean-up time will fall within what interval about the mean? State the lower and upper limits of the interval.
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! Mean=72 hours
SD=8 hours, square root of variance
56 hours is 2 SDs below the mean.
0.0228 or 2.28% of the time, it will be fewer than 56 hours
97.72% of the time, it will be greater than or equal to 56 hours.
95% of the time is +/- 1.96 SDs or 15.68 hours
CI is (56.32,87.68) units are hours.
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