During a test period,an experimental group of 10 vehicles using an 85 percent ethanol-gasoline mixture showed mean CO2 emissions of 667 pounds per 1000 miles,with a standard deviation of 20 pounds.A control group of 14 vehicles using regular gasoline showed mean CO2 emissions of 679 pounds per 1000 miles with a standard deviation of 15 pounds.Assuming equal variances,the pooled variance is
A)296.59
B)225.00
C)400.00
D)522.16

Question

Quizplus · Accepted Answer

The pooled variance is calculated as:s^2 = ((n1-1)*s1^2 + (n2-1)*s2^2) / (n1 + n2 - 2)where n1 and n2 are the sample sizes, s1 and s2 are the sample standard deviations.Plugging in the values, we get:s^2 = ((10-1)*20^2 + (14-1)*15^2) / (10 + 14 - 2) = 296.59Therefore, the pooled variance is 296.59.

During a Test Period,an Experimental Group of 10 Vehicles Using