Tensile strength tests were carried out on two different grades of wire rod resulting in the accompanying data:

Grade Sample Size Sample Mean (kg/mm2) Sample Standard Deviation

1064 31 108 1.3

1078 31 124 1.6

Do the data provide compelling evidence (at =0.05 ) for concluding that true average strength for the 1078 grade exceeds that for the 1064 grade? Show all your work.

Estimate the difference between true average strengths for the two grades with a 95% confidence interval (show all your work). Interpret this confidence interval.