An article in Fire Technology investigated two different foam expanding agents that can be used in the nozzles of fire-fighting spray equipment. A random sample of five observations with an aqueous film-forming foam (AFFF) had a sample mean of 4.7 and a standard deviation of 0.6. A random sample of five observations with alcohol-type concentrates

(ATC) had a sample mean of 6.9 and a standard deviation 0.8.

(a) Can you draw any conclusions about differences in mean foam expansion? Assume that both populations are well represented by normal distributions with the same standard deviations.

(b) Find a 95% confidence interval on the difference in mean foam expansion of these two agents.