SOLUTION: 7. For a random variable that is normally distributed, with mean of 80 and standard deviation of 10, determine the probability that a simple random sample of 25 items will have a m
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Question 1160711: 7. For a random variable that is normally distributed, with mean of 80 and standard deviation of 10, determine the probability that a simple random sample of 25 items will have a mean that is; A. greater than 78. B. between 79 and 85. C. less than 85. Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! z=(x-mean)/sigma/sqrt(n), and SE is 10/sqrt(25)=2
so this becomes a normal diet with mean 80 and sd 2
a. greater than 78 is a z>-1 or prob. 0.8413
b. between 79 and 85 is z > -0.5 and +2.5 or probability 0.6853
c. z less than 2.5 is probability 0.9938.
