Chapter 13.4, Problem 13E

One portion of the research described in a paper by Yean-Jye Lu5 involved an evaluation of maneuver times for vehicles of various sizes that were involved in making a left turn at an intersection with a separate left-turn lane but without a separate left-turn phase on the traffic light governing the intersection (an “unprotected” left-turn maneuver). The maneuver time was measured from the instant that a vehicle entered the opposing lanes of traffic until it completely cleared the intersection. Four-cylinder automobiles were classified as “small cars” and sixor eight-cylinder automobiles as “large cars.” Trucks and buses were combined to form a third category identified as “truck or bus.” Other motorized vehicles (motorcycles, etc.) were ignored in the study. A summary of the data, giving maneuver times (in seconds) for vehicles that attempted the left-turn maneuver from a standing stop, appears in the accompanying table.

a Is there sufficient evidence to claim that the mean maneuver times differ for the three vehicle types? Give bounds for the attained significance level.

b Indicate the appropriate conclusion for an α = .05 level test.