Chapter 9, Problem 18SE

The Williamsburg Bridge is a suspension bridge that spans the East River, connecting the boroughs of Brooklyn and Manhattan in New York City. An assessment of the strengths of its cables is reported in the article “Estimating Strength of the Williamsburg Bridge Cables” (R. Perry, The American Statistician. 2002:211–217). Each suspension cable consists of 7696 wires. From one of the cables, wires were sampled from 128 points. These points came from four locations along the length of the cable (I, II, III, IV). At each location there were eight equally spaced points around the circumference of the cable (A, B, C, D, E, F, G, H). At each of the eight points, wires were sampled from four depths: (1) the external surface of the cable, (2) two inches deep. (3) four inches deep, and (4) seven inches deep (the cable is 9.625 inches in radius). Under assumptions made in the article, it is appropriate to consider this as a two-factor experiment with circumferential position and depth as the factors, and with location providing four replicates for each combination of these factors. The minimum breaking strength (in lbf) is presented in the following table for each of the 128 points.