A sports writer wished to see if a football filled with helium travels farther, on average, then a football filled with air. To test this, the writer used 18 adult male volunteers. These volunteers were randomly divided into two groups of nine subjects each. Group 1 kicked a football filled with helium to the recommended pressure. Group 2 kicked a football filled with air to the recommended pressure. The mean yardage for group 1 was x 1 = 30 yards, with a standard deviation s1 = 8 yards. The mean yardage for group 2 was x 2 = 26 yards, with a standard deviation s2 = 6 yards Assume the two groups of kicks are independent. Let 1 and 2 represent the mean yardage we would observe for the entire population represented by the volunteers if all members of this population kicked, respectively, a helium and an air-filled football. Assume that two sample t procedures are safe to use.

Find the 99% confidence interval for 1 - 2. Interpret the result in the context of the study and what do you conclude?