During oil drilling operations, components of the drilling assembly may suffer from sulde stress cracking, An article reported on a study in which the composition ofa standard grade of steel was analyzed. T x = yield strength (MPa) was read from a graph in the article (which also included the equation of the least squares line). I 634 643 712 709 837 820 010 870 856 923 878 937 948 I-E-I\" 2x, = 10,577, 2y, = 898, Zx = 8,743,221, 2y} = 66,912, ley, = 706,149 (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.) (b) Compute the estimated standard deviation SB . (Round your answer to four decimal places.) 1 s, =1: 1 (c) Calculate a condence 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.) (EVE) Does it appear that this true average change has been precisely estimated? 0 This is a fairly wide interval, so e has been precisely estimated. 0 This is a fairly wide interval, so 171 has not been precisely estimated. 0 This is a fairly wide interval, so #1 has been precisely estimated. 0 This is a fairly narrow interval, so u has not been precisely estimated, 0 This is a fairly narrow interval, so '71 has been precisely estimated