Mechanical engineers have developed a new high-strength aluminum alloy for use in antisubmarine aircraft, tankers, and long-range bombers. (JOM, Jan. 2003.) The new alloy is obtained by applying a retrogression and re aging (RAA) heat treatment to the current strongest aluminum alloy. A series of strength tests were conducted to compare the new RAA alloy to the current strongest alloy. Three specimens of each type of aluminum alloy were produced and the yield strength (measured in mega-pascals, MPa) of each specimen determined. The results are summarized in the table.

a. Estimate the difference between the mean yield strengths of the two alloys using a 95% confidence interval.
b. The researchers concluded that the RAA-processed aluminum alloy is superior to the current strongest aluminum alloy with respect to yield strength. Do you agree?

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Alloy Type RAA Current Number of specimens 3 3 Mean yield strength (MPa) 641.0 592.7 Standard deviation 19.3 12.4