Refer to Exercise 1.30 (p. 28) and the data on structurally deficient highway bridges compiled by the Federal Highway Administration (FHWA) into the National Bridge Inventory (NBI). For each state, the NBI lists the number of structurally deficient bridges and the total area (thousands of square feet) of the deficient bridges. The data for the 50 states (plus the District of Columbia and Puerto Rico) are saved in the file. (The first five and last five observations are listed in the table in the next column.)
For future planning and budgeting, the FHWA wants to estimate the total area of structurally deficient bridges in a state based on the number of deficient bridges.

a. Write the equation of a straight-line model relating total area (y) to number of structurally deficient bridges (x).
b. The model, part a, was fit to the data using Minitab, as shown below. Find the least squares prediction equation on the printout.
c. List the assumptions required for the regression analysis.
d. Locate the estimated standard error of the regression model, s, on the printout.
e. Use the value of s to find a range where most (about 95%) of the errors of prediction will fall.

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Area (thousands of sq. ft.) State Number Alabama Alaska Arizona Arkansas 1,899 155 181 997 432.7 60.9 110.5 347.3 California 3,140 5,177.9 Washington West Virginia Wisconsin Wyoming Puerto Rico 400 502.0 331.5 399.8 143.4 195.4 1,058 1,302 389 241 Regression Analysis: SDArea versus NumberSD Analysis of variance DF Adj se Begrassion 1 12710141 12716141 31.50 50 2017311: 51 3203252 Adj MS F-Value p-value 0.000 Source 103462 Error Total Nodel Bumnary * R-g R-qtadj) 37.43 435.107 18.65 Coetticients Coef SE Coef T-Value p-value 123 Term 0.97 0.335 120 MumbereD 0.3456 Conatant 0.0616 5.61 0.000 Begrassion Equation SDArea 120 + 0.3456 NumberBD