The test statistic for difference between two means is given by:
Thus, the appropriate test statistic is given by:
At 10% level of significance, the rejection region is given by
where: for 10% level of significance is 1.65
Since z = 1.66 > , we reject the null hypothesis, which means that <span>the traffic control strategy does not reduce carbon monoxide concentrations by at least 2 ppm.</span>