A study looked at the effect of mean ozone exposure on change in pulmonary function. Fifty hikers were recruited into the study; 25 study participants hiked on days with lowozone exposure, and 25 hiked on days with highozone exposure. The change in pulmonary function after a 4hour hike was recorded for each participant. The results are given in the table below. Ozone level Mean FEV change sd 11 High 0.101 0.253 25 Low 0042 0.106 25