(6 Pts) The amount of time that customers wait in line during peak hours at one
ID: 3329807 • Letter: #
Question
(6 Pts) The amount of time that customers wait in line during peak hours at one bank is normally distributed with a mean of 14 minutes and a standard deviation of 3 minutes. Using StatCrunch: a) Find the probability that waiting time is between 17 and 19 minutes. b) Find the probability that waiting time is less than 10 minutes. (7 Pts) A study is being planned to estimate the mean number of semester hours taken by students at a college. The population standard deviation is 4.7 hours. How many students should be included in the sample to be 95% confident that the sample mean is within 2 semester hours of the population mean, , for all students at this college?Explanation / Answer
Answer to the question is as below:
1)
Mean = 14
Stdev = 3
a. P(17<X<18) = P(17-14/3<Z<18-14/3)
= P(1<Z<1.33)
= .9082-.8413
= .0669
b. P(X<10)
= P(Z<10-14/3)
= P(Z<-1.33)
= 1-.9082
= .0918
2)
Stdev = 4.7
MOE = 2 <= Z*Sigma/sqrt(N)
hence, Rearranging will give :
N >= (Z*Stdev/2)^2 = (1.96*4.7/2)^2 = 21.21
So, answer is 22
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