Suppose we determine a 95% CI for the true mean change in pulmonary function on high-ozone days.

Question:

Suppose we determine a 95% CI for the true mean change in pulmonary function on high-ozone days. Is this CI narrower, wider, or the same width as a 90% CI? (Do not actually compute the CI.)

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.

Table 8.18: Comparison of change in FEV on highozone vs. low-ozone days

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