Question

14.50 Impact of red light cameras on car crashes. Refer to the 0 June 2007 Virginia Department of Transportation (VDOT) REDUIT study of a newly adopted photo-red-light enforcement pro- gram, Exercise 9.53 (p. 464). Recall that the VDOT pro- vided crash data both before and after installation of red light cameras at several intersections. The data (measured as the number of crashes caused by red light running per in- tersection per year) for 13 intersections in Fairfax County, Virginia, are reproduced in the next table below. The VDOT wants to determine if the photo-red enforcement program is effective in reducing red-light-running crash in- cidents at intersections. Use the nonparametric Wilcoxon signed rank test and the accompanying MINITAB print- out) to analyze the data for the VDOT. Wilcoxon Signed Rank Test: Difference Test of median - 0.000000 versus median > 0.000000 Nfor Wilcoxon Estimated Test Statistic P Median 13 79.0 0.0110 .9650 Difference 13

Answer 1

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. We have to take absolute difference between these pajts Anak ection. L Before T after T sian Tarsolute Root camera difference when Vartots Camera 1:35 lo + + + + + 3.60 40.27 0.29 4.55 2.60 2. 29 2.40 0.73 B.15 3.21 0.88 1.35 7.85 1.79 2.04 3.14 2 .72 0.24 1.57 0.43 0,28 1.09 4.92 2. 24 0.27 0.29 2-76 0.56 0.85 0.32 0.49 1.58 2-78 0.6 0.26 2-43 احمدی به فن به ادما بدا - + + 12

IW =67. Wetit(2=0.05,12, two. sideel.) -13- TWI7 Wrait Reject Ho at sdo 1.0.5. & we conclude that The photo-red enforcement proqtamis effective in reducing sed light sunding Ceash Theidente con intersection Also, oftio are output value of pise which also indicates that Pvalue 20.05 1 & fail to accept Ho at slo 1.O.S. & I conclude that the photo red enforcer program is effective is deducina seda dunning Crash incidents at intersec The software outputs are valid as mannued interpeelections.