Solved: The average life of a bread-making machine is 7
Chapter 9, Problem 8.25(choose chapter or problem)
The average life of a bread-making machine is 7 years, with a standard deviation of 1 year. Assuming that the lives of these machines follow approximately a normal distribution, nd (a) the probability that the mean life of a random sample of 9 such machines falls between 6.4 and 7.2 years; (b) the value of x to the right of which 15% of the means computed from random samples of size 9 would fall.
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