Fast Food Wait Times

skyguy

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Joined
Sep 11, 2006
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Suppose it is known that the time spent by customers in a fast-food restaurant is a normally distributed variable with a mean of 25 minutes and a standard deviation of 8 minutes. What is the probability that a random sample of 20 customers will yield a mean between 23 and 28 minutes, inclusive?
 
Do you have any idea?.

Use the sample distribution of the sample mean.

\(\displaystyle \L\\\frac{x-{\mu}}{\frac{\sigma}{\sqrt{n}}}\)

Use x=23 and 28. Find their probabilities and subtract them.
 
first find the propability of between 23 and 28 then turn it into a binomial with n=20
 
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