A materials scientist is evaluating the tensile strength of two newly developed carbon-fiber composites: 'Aeroflex' and 'Durawave'. The scientist believes that Aeroflex has a mean tensile strength that is more than 50 MPa greater than that of Durawave.
A random sample of 200 specimens of Aeroflex found a mean tensile strength of 3452 MPa with a standard deviation of 78 MPa.
A random sample of 250 specimens of Durawave found a mean tensile strength of 3384 MPa with a standard deviation of 72 MPa.
Stating your hypotheses clearly, test the scientist's claim at the 5% level of significance.
State whether it was necessary to assume that the tensile strengths of the specimens are normally distributed. Give a reason for your answer.
