Question

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 statement will calculate the margin of error?

	a.	=9-8.5
	b.	=9-5
	c.	=8.5-5
	d.	=1.96*3/SQRT(45)
	e.	=1.96*9/SQRT(45)
	f.	None of the above.

Answer 1

Solution :

Given that,

Point estimate = sample mean = = 8.5

variance = 9

Population standard deviation = = 3

Sample size = 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

Margin of error = E = Z_/2* ( /n) = =1.96 * 3 / SQRT(45)