A study was trying to determine if two methods were equally effective in reducing average heart rate of "stressed" patients. Summary statistics for the two groups follow, where the reduction in heart rate in beats per minute (bpm) of the resting heart rate was recorded after 4 weeks of using the two methods:

1. Find the 99% confidence interval for (?A ? ?B).
2. Interpret your interval in terms of the problem.
3. What is the smallest significant difference suggested by your interval from (c)? Explain your answer.
4. What is someone says, "For the confidence interval in (a), we needed to assume the population standard deviations of both groups were equal". Do you happen to agree? Explain.

Group A B Sample Mean 6.3 4.1 Sample Standard Deviation 5.2 2.5 Sample Size 31 45