One-hour carbon monoxide concentrations in 43 air samples from a section of a city showed an average of 11.6 ppm and a standard deviation of 7.08. after a traffic control strategy was put into place, 19 air samples showed an average carbon monoxide concentration of 6.4 ppm and a standard deviation of 6.94. it is known that carbon monoxide concentrations are normally distributed. the state will adopt the traffic control strategy on a large scale if there is evidence that it reduces carbon monoxide concentrations by at least 2 ppm. with h_0: \mu_1-\mu_2=2; \ \ \ h_a: \mu_1-\mu_2> 2 h 0 : μ 1 − μ 2 = 2 ; h a.μ 1 − μ 2 > 2 the appropriate test statistic is . at the 10% level of significance, we , which means that .