Answer Happy

During oil drilling operations, components of the drilling assembly may suffer from sulfide stress cracking. An article reported on a study in which the composition of a standard grade of steel was analyzed. The following data on y = threshold stress (% SMYS) and x = yield strength (MPa) was read from a graph in the article (which also included the equation of the least squares line). X 636 643 710 707 835 820 810 870 856 923 878 937 948 y 100 94 89 83 76 75 74 63 57 55 47 43 38 Σχ; = 10,573, ΣΥ ;=894, x² = = 8,736,741, Σy = 66,268, Exiy; = 702,761 = (a) What proportion of observed variation in stress can be attributed to the approximate linear relationship between the two variables? (Round your answer to four decimal places.) X (b) Compute the estimated standard deviation S₁ (Round your answer to four decimal places.) s B1 S = X B1 (c) Calculate a confidence interval using confidence level 95% for the expected change in stress associated with a 1 MPa increase in strength. (Round your answers to three decimal places.) X Does it appear that this true average change has been precisely estimated? O This is a fairly narrow interval, so ßo has not been precisely estimated. O This is a fairly wide interval, so ₁ has been precisely estimated. 1 This is a fairly wide interval, so ß, has not been precisely estimated. O This is a fairly narrow interval, so ₁ has been precisely estimated. O This is a fairly wide interval, so ß has been precisely estimated.