Refer to the International Journal of Forest Engineering (July 1999) study of the attributes of forest access roads in Ireland, Exercise 7.110. Recall that the transient surface deflection (millimeters) was measured for independent random samples of 32 mineral subgrade access roads and 40 peat subgrade access roads. The results are reproduced in the accompanying table.

a. Compare the surface deflection variances of the two pavement types with a two-tailed test of hypothesis using α = .05.

b. In Exercise 7.110, you used a 95% confidence interval to compare the surface deflection variances. Demonstrate that the inferences derived from the test and confidence interval are identical. Will this always be the case? Explain.

Data from Exercise 7.110

In Ireland, the majority of commercial forests are located in remote areas on predominantly peat soils. These roads exhibit rapid deterioration when traversed by logging vehicles or other heavy machinery. A study of the attributes of forest access roads in Ireland was published in the International Journal of Forest Engineering (July 1999). One measure of the strength of pavement is transient surface deflection— the higher the surface deflection, the weaker the pavement. The type of pavement (mineral subgrade or peat subgrade) was determined for a sample of 72 forest access roads, then each was analyzed for surface deflection (measured in millimeters).

Transcribed Image Text:

Pavement Subgrade Mineral Peat Number of Roads 32 40 Mean Surface Deflection (mm) 1.53 3.80 Standard Deviation 3.39 14.3