• 10-18. An article in Fire Technology investigated two dif- ferent foam expanding agents that can be used in the nozzles of fire-fighting spray equipment. A random sample of five ob- servations 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. Find a 95% confidence interval on the difference in mean foam expansion of these two agents. Can you draw any con- clusions about which agent produces the greatest mean foam expansion? Assume that both populations are well represented by normal distributions with the same standard deviations.