The Canadian Journal of Civil Engineering (January 2013) published a study of the optimal layout (design) of streets in a neighborhood to maximize road safety. Five different community road patterns were compared: (1) traditional grid, (2) fused grid, (3) cul-de-sac, (4) Dutch sustainable road safety (SRS), and (5) 3-way offset. A sample of 30 neighborhoods was selected for each type of road pattern, resulting in a total sample size of 150. Road safety was measured as the number of collisions over a 3-year period. The researchers found that this variable follows a negative binomial distribution rather than a normal distribution; consequently, they analyzed the data using the nonparametric Kruskal-Wallis H-test. The rank sums for the 5 road patterns are provided here.

a. Specify the null and alternative hypotheses for this nonparametric test.
b. The researchers reported the test statistic as H = 71.53. Verify this calculation.
c. State the appropriate conclusion at α = .05?

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Dutch 3-Way Traditional Fused Fused Grid Cul-de- Sac 3-Way Offset Grid 3398 SRS Rank Sum 2249.5 1288.5 3144 1245