1. Let X denote the Brinell hardness measurement of ductile iron sub-critically annealed. Assume X~ N(u, 6 30). We are interested in testing the hypotheses: Ho: u = 115 H1: u > 115 using n=25 observations of X. a) Define the test statistic and the decision rule for this test. b) A random sample of size 25 observations of X yielded measurements with mean of 127.9. Compute the value of the test statistic and clearly give your conclusion