An article in Fire Technology describes the investigation of two different foam expanding agents that can be used in the nozzles of firefighting spray equipment. A random sample of five observations with an aqueous film-forming foam (AFFF) had a sample mean of 4.340 and a standard deviation of 0.508. A random sample of five observations with alcoholtype concentrates (ATC) had a sample mean of 7.091 and a standard deviation of 0.430. Assume that both populations are well represented by normal distributions with the same standard deviations.
(a) Is there evidence to support the claim that there is no difference in mean foam expansion of these two agents? Use a fixed-level test with
α = 0.10.
(b) Calculate the P-value for this test.
(c) Construct a 90% CI for the difference in mean foam expansion. Explain how this interval confirms your finding in part (a).