What test can be used to determine whether the mean change in FEV differs between the high-ozone

Question:

What test can be used to determine whether the mean change in FEV differs between the high-ozone and low-ozone days?

Pulmonary Disease

A study was performed looking 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 high-ozone exposure. The change in pulmonary function after a 4-hour hike was recorded for each participant. The results are given in Table 8.18.

Ozone level Mean change in FEV sd High Low 0.101 25 0.253 0.042 0.106 25