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

Multiple Choice

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.At α = .05,in a left-tailed test,the critical value to compare the means (assuming equal variances) is

A) −2.508
B) −2.074
C) −1.321
D) −1.717