Refer to the Landscape Ecology Engineering (January 2013) investigation of the impact of soil scouring on the characteristics of overturned and uprooted trees, Exercise 14.12. Recall that a completely randomized design was employed with three treatments (scouring conditions): no scouring (NS), shallow scouring (SS), and deep scouring (DS). Five medium-sized trees were uprooted in each condition and the maximum resistive bending moment at the trunk base (kilo Newton-meters) was measured for each tree. The data are reproduced in the following table.

a. Verify that one or more of the assumptions of the ANOVA F test conducted in Exercise 14.12 may be violated.

b. Conduct the appropriate nonparametric test at α = .05. Does soil scouring impact the location of the distribution of maximum resistive bending moment at the tree trunk base?

Data from Exercise 14.12

Trees that grow in flood plains are susceptible to overturning. This is typically due to floodwaters exposing the tree roots (called soil scouring). Environmental engineers at Saitama University (Japan) investigated the impact of soil scouring on the characteristics of overturned and uprooted trees (Landscape Ecology Engineering, January 2013). Tree pulling experiments were conducted in the floodplains of the Komagama river. Trees were randomly selected to be uprooted in each of three areas that had different scouring conditions: no scouring (NS), shallow scouring (SS), and deep scouring (DS). During the uprooting of the trees, the maximum resistive bending moment at the trunk base (kilo Newton-meters) was measured.

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SCOURING None Shallow Deep 23.68 11.13 4.27 8.88 29.19 2.36 7.52 13.66 8.48 25.89 20.47 12.09 22.58 23.24 3.46