1. Tensile strength tests were carried out on two different grades of wire rod resulting in the accompanying data:
Grade Sample Size Sample Mean Sample St. Dev.
1064 m= 130 xbar= 108 s1= 1.3
1078 n= 130 ybar= 124 s2= 2.0
a. Does the data provide compelling evidence for concluding that true average strength for the 1078 grade exceeds that for the 1064 grade by more than 10 ? Test the appropriate hypotheses using the -value approach.
b. To estimate the difference between true average strengths for the two grades in a way that provides information about precision and reliability, determine the 95% confidence interval for the difference between the two grades.