No-fines concrete, made from a uniformly graded coarse aggregate and a cement-water paste, is beneficial in areas prone to excessive rainfall because of its excellent drainage properties. An article cited a study that employed a least squares analysis in studying how y = porosity (%) is related to x = unit weight (pcf) in concrete specimens. Consider the following representative data: x 99.0 101.1 102.7 103.0 105.4 107.0 108.7 110.8 21.5 20.9 19.6 y 28.8 27.9 27.0 25.2 22.8 X 112.1 112.4 113.6 113.8 115.1 115.4 120.0 13.0 13.6 10.8 y 17.1 18.9 16.0 16.7 a. (50 points) Determine the equation of the estimated regression line. b. (5 points) Calculate a point estimate for true average porosity when unit weight is 111. c. (15 points) What proportion of the observed variation in efficiency ratio can be attributed to the simple linear regression relationship between the two variables?
