An engineer who is studying the tensile strength of a steel
alloy knows that tensile strength is approximately normally
distributed with sigma= 60 psi. A random sample of 12 specimens has
a mean tensile strength of 3450 psi.
a) Compute a two-side confidence interval on the maen tensile
strength at a 95% confidence level.
b) Test the hypothesis that the mean strength is 3500 psi at
alfa=0.05, and provide a conclusion statement.
c) If we keep the signifiance level constant...