Chapter 8.4, Problem 8.54ACI

Traffic sign maintenance. The Federal Highway Administration (FHWA) recently issued new guidelines for maintaining and replacing traffic signs. Civil engineers at North Carolina State University conducted a study of the effectiveness of various sign maintenance practices developed to adhere to the new guidelines and published the results in the Journal of Transportation Engineering (June 2013). One portion of the study focused on the proportion of traffic signs that fail the minimum FHWA retroreflectivity requirements. Of 1,000 signs maintained by the North Carolina Department of Transportation (NCDOT), 512 were deemed failures. Of 1,000 signs maintained by county-owned roads in North Carolina, 328 were deemed failures. Conduct a test of hypothesis to determine whether the true proportions of traffic signs that fail the minimum FHWA retroreflectivity requirements differ depending on whether the signs are maintained by the NCDOT or by the county. Test using α = .05.