Road safety of neighborhoods. 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 KruskalWallis H-test. The rank sums for the 5 road patterns are provided here. Traditional Grid Fused Grid Cul-deSac Dutch SRS 3-Way Offset Rank Sum 3398 2249.5 3144 1288.5 1245

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 a = .05.