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 using the formula:pooled variance = [(n1 - 1) * s1^2 + (n2 - 1) * s2^2] / (n1 + n2 - 2)where n1 and n2 are the sample sizes, and s1 and s2 are the sample standard deviations.Plugging in the values from the question, we get:pooled variance = [(10 - 1) * 20^2 + (14 - 1) * 15^2] / (10 + 14 - 2)= [1800 + 3150] / 22= 4950 / 22= 225.00Therefore, the pooled variance is 225.00.

During a Test Period, an Experimental Group of 10 Vehicles