(c) Calculate a 95% condence interval for the difference between the means (t critical value is 2.069]. (-4 points } 2. A stud}r looked at the effect of mean ozone exposure on change in pulmonary function. Fifty hikers were recruited into the study; 25 stud}.r participants hiked on days with low-ozone exposure, and 25 hiked on days with high-ozone exposure. The change in pulmonaryr function after a 4-hour hike was recorded for each participant. The results are given in the table below. Ozone level Mean FEV change sd n High 0.101 0.253 25 Low 0042 0.106 25 (a) Calmilate the pooled estimate of variance. (4 points ) (h) Calculate the value of the t-test statistic, and give its degrees of freedom.(4 points ]