Refer to Exercise 10.79 and the straight-line model relating the mean shear strength E(y) of masonry joints to pre compression stress, x. To test this model, a series of stress tests were performed on solid bricks arranged in triplets and joined with mortar (Proceedings of the Institute of Civil Engineers, Mar. 1990). The pre compression stress was varied for each triplet, and the ultimate shear load just before failure (called the shear strength) was recorded. The stress results for seven triplets (measured in N/mm²) are shown in the next table. Conduct a nonparametric test of H_o: β₁ = 0 against the alternative H_o: β₁ > 0. Test using α = .05.

Data from Exercise 10.79

In response to a health advisory regarding mercury poisoning in Maine lakes, the Environmental Protection Agency conducted a field study of 120 Maine lakes. (Statistical Case Studies: A Collaboration between Academe and Industry, American Statistical Association, 1998.) In addition to the mercury level (parts per million) of each lake, the EPA measured the lake elevation (feet). The data are saved in the MAINELAKE file.

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TRIPLETS Triplet Test 1 2 3 4 5 6 7 Shear 1.00 2.18 2.24 2.41 2.59 2.82 3.06 strength, y Precompression 0 .60 1.20 1.33 1.43 1.75 1.75 stress, x