The article Effect of Internal Gas Pressure on the Compression Strength of Beverage Cans and Plastic Bottles (J. Testing Eval., 1993: 129-131) includes the accompanying data on compression strength (lb) for a sample of 12-oz aluminum cans lled with strawberry drink and another sample lled  with cola. Does the data suggest that the extra carbonation of cola results in a higher average compression strength? Base your answer on a P-value. What assumptions are necessary for your analysis?

a. Verify graphically that normality is an appropriate assumption.

b. Calculate a 99% con dence interval for the population difference in mean volumes.

c. Does the upper limit of your interval in (b) give a 99% lower confidence bound for the difference between the two m s? If not, calculate such a bound and interpret it in terms of the relationship between the foam volumes of Coke and Pepsi.

d. Summarize in a sentence what you have learned about the foam volumes of Coke and Pepsi.