Question

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	645	712	707	837	820	810	870	856	923	878	937	948
y	100	92	89	83	76	75	74	63	57	55	47	43	38

x_i = 10,579,    

y_i = 892,    

x_i² = 8,745,505,     

y_i² = 65,896,    

x_iy_i = 701,989

(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.)

answer: 0.8906

(b)Compute the estimated standard deviation

s_{1= __________________}

(Round your answer to four decimal places.)

(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.)

( , )

Please answer b and c.

Answer 1

Thank you