SOLUTION: The daily cost of photocopying in a certain office is assumed to be normally distributed with a mean of $80 and a standard deviation of $4. Find the probability that:
a) the cost
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Question 229988: The daily cost of photocopying in a certain office is assumed to be normally distributed with a mean of $80 and a standard deviation of $4. Find the probability that:
a) the cost for a randomly selected day is more than $75 -----> = 0.8944
b) the average cost of 10 randomly selected days is more than $75
Stuck with part b, should it just be 0.8944^10?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The daily cost of photocopying in a certain office is assumed to be normally distributed with a mean of $80 and a standard deviation of $4. Find the probability that:
a) the cost for a randomly selected day is more than $75 -----> = 0.8944
b) the average cost of 10 randomly selected days is more than $75
Stuck with part b, should it just be 0.8944^10?
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Comment: Part "a" is a population problem where the mean is u and std = sigma
Part "b" is a sample-means problem where the mean of the sample means is u but std = sigma/sqrt(n)
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Part "b":
z(75) = (75-80)/(4/sqrt(10)) = -3.9528
---
P(x-bar > 75) = P(z > -3.9528) = 0.9999..
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Cheers,
Stan H.
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