# Comparing Variances Question Help

• Nov 8th 2011, 04:50 PM
youngb11
Comparing Variances Question Help
The McBurger company's management is interested in whether there is a difference in the standard deviation in services times for customers who use the drive-through window versus those who go inside to the service counter. A sample of $13$ drive-through customers and a sample of $9$ inside-counter customers were selected. The time (minutes) it took for each customer to be served was recorded. The following statistics are computed:
$Drive-through: mean = 4.5, s = 2.0$
$Insider-counter: mean = 4.0, s = 1.2$

Based on a significance level of $0.10$, determine if there is a difference in the standard deviation in service time.

I'm assuming null hypothesis is var(drivethrough)/var(insider) = 1 and alternative hypothesis is var(drivethrough)/var(insider) /= 1, but I'm not sure of what to do after this. If anyone could post the steps I'll try to follow along, thanks!
• Nov 8th 2011, 08:50 PM
CaptainBlack
Re: Comparing Variances Question Help
Quote:

Originally Posted by youngb11
The McBurger company's management is interested in whether there is a difference in the standard deviation in services times for customers who use the drive-through window versus those who go inside to the service counter. A sample of $13$ drive-through customers and a sample of $9$ inside-counter customers were selected. The time (minutes) it took for each customer to be served was recorded. The following statistics are computed:
$Drive-through: mean = 4.5, s = 2.0$
$Insider-counter: mean = 4.0, s = 1.2$

Based on a significance level of $0.10$, determine if there is a difference in the standard deviation in service time.

I'm assuming null hypothesis is var(drivethrough)/var(insider) = 1 and alternative hypothesis is var(drivethrough)/var(insider) /= 1, but I'm not sure of what to do after this. If anyone could post the steps I'll try to follow along, thanks!

F or variance ratio test.

1.3.5.9. F-Test for Equality of Two Standard Deviations

CB