Question

# 5. a.) A random sample of 45 door-to-door salespersons were asked how long on average they...

5.

a.)

A random sample of 45 door-to-door 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 =8.5-1.96*9/SQRT(45)

b.

=8.5+1.96*3/SQRT(45), and =8.5-1.96*3/SQRT(45)

c.

=45+1.96*3/SQRT(9), and =45-1.96*3/SQRT(9)

d.

=45+0.95*3/SQRT(9), and =45-0.95*3/SQRT(9)

e.

None of the above.

A random sample of 45 door-to-door 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?

 a. 45 salespersons b. 9 minutes c. 8.5 minutes d. 5 minutes e. None of the above.

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 = Z0.025 = 1.96

+ / -  Z/2* ( /n)

 .b = 8.5+1.96*3/SQRT(45), and =8.5-1.96*3/SQRT(45) Option b) is correct. (b) = 8.5 The point estimate for the average conversation length = 8.5 minutes .