Refer to Exercise 14.19. Use a multiple comparisons procedure to compare the mean crack widths for the four wetting periods. Identify the means that appear to differ. Use α = .05.

Data from Exercise 14.19

The Perth (Australia) Metropolitan Water Authority recently completed construction of a land pipeline for transporting domestic wastewaters from a primary treatment plant. During construction, the cement mortar lining of the pipeline was tested for cracking to determine whether autogenous healing will seal the cracks. Otherwise, expensive epoxy filling repairs would be necessary (Proceedings of the Institute of Civil Engineers, Apr. 1986). After cracks were observed in the pipeline, it was kept full of water for a period of 14 weeks. At each of 12 crack locations, crack widths were measured (in millimeters) after the 2nd, 6th, and 14th weeks of the wet period, as shown in the table. The data were subjected to an ANOVA using SAS. The SAS printout is shown below. Conduct a test to determine whether the mean crack widths differ for the four time periods. Test using α = .05.

CRACKPIPE Crack Width After Wetting Crack Width After Wetting crack Location o weeks 2 Weeks 6 Weeks 14 Weeks Crack Location o Weeks 2 Weeks 6 Weeks 14 Weeks 1 50 .20 .10 .10 7 90 25 .05 .05 2 40 .20 .10 .10 1.00 .30 .05 .10 3 .60 .30 .15 .10 9 .70 25 .10 .10 .80 40 .10 .10 10 .60 .25 .10 .05 5 .80 30 .05 .05 11 .30 .15 .10 .05 6 1.00 40 .05 .05 12 .30 .14 05 .05 4)