5.
a.)
A random sample of 45 doortodoor salespersons were asked how long on average they were able to talk to the potential customer. Their answers revealed a mean of 8.5 minutes with a variance of 9 minutes. Which Excel statements will construct a 95% confidence interval for the time it takes a salesperson to talk to a potential customer.
a. 
=8.5+1.96*9/SQRT(45), and =8.51.96*9/SQRT(45) 

b. 
=8.5+1.96*3/SQRT(45), and =8.51.96*3/SQRT(45) 

c. 
=45+1.96*3/SQRT(9), and =451.96*3/SQRT(9) 

d. 
=45+0.95*3/SQRT(9), and =450.95*3/SQRT(9) 

e. 
None of the above. A random sample of 45 doortodoor salespersons were asked how long on average they were able to talk to the potential customer. Their answers revealed a mean of 8.5 minutes with a variance of 9 minutes. What is the point estimate for the average conversation length?

5)
Solution :
(a)
Given that,
= 8.5
^{2} = 9
= 3
n = 45
At 95% confidence level the z is ,
= 1  95% = 1  0.95 = 0.05
/ 2 = 0.05 / 2 = 0.025
Z_{/2} = Z_{0.025} = 1.96
+ /  Z_{/2}* ( /n)
.b 
= 8.5+1.96*3/SQRT(45), and =8.51.96*3/SQRT(45) Option b) is correct. (b) = 8.5 The point estimate for the average conversation length = 8.5 minutes . 
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