4.8 The tensile strength of a fiber using in manufacturing cloth is of interest to the purchaser. Previous experience indicates that the standard deviation of tensile strength is 2psi. A random sample of eight fiber specimens is selected, and the average tensile strength is found to be 127 psi. (a) Test the hypothesis that the mean tensile strength equals 125 psi versus the alternative that the mean exceeds 125 psi. Use a= 0.05. (b) What is the P-value for this test? (d) Construct a 95% lower confidence interval on the mean tensile strength