The article “Flexure of Concrete Beams Reinforced with Advanced Composite Orthogrids” (J. of Aerospace Engr., 1997: 7–15) gave the accompanying data on ultimate load

(kN) for two different types of beams.

Sample Sample Sample Type Size Mean SD Fiberglass grid 26 33.4 2.2 Commercial 26 42.8 4.3 carbon grid

a. Assuming that the underlying distributions are normal, calculate and interpret a 99% CI for the difference between true average load for the fiberglass beams and that for the carbon beams.

b. Does the upper limit of the interval you calculated in part

(a) give a 99% upper confidence bound for the difference between the two s? If not, calculate such a bound.

Does it strongly suggest that true average load for the carbon beams is more than that for the fiberglass beams?

Explain.