Question

Use the following to answer questions 4-6:

A sports writer wished to see if a football filled with helium travels farther, on average, than 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 = 30 yards with a standard deviation s1 = 8 yards. The mean yardage for group 2 was1

x2 = 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.

4. A 99% confidence interval for 1 – 2 is (use the conservative value for the degrees of freedom)

1. A) 4 ± 4.7 yards.

2. B) 4 ± 6.2 yards.

3. C) 4 ± 7.7 yards.

4. D) 4 ± 11.2 yards.

Ans: D (please show me how to get it tho)

Answer 1

from above 99% CI =estimate -/+ margin of error =4 -/+11.2