A driver's ability to detect highway signs is an important consideration in highway safety. In his dissertation, Highway Construction Safety and the Aging Driver, S. Younes investigated the distance at which drivers can first detect highway caution signs. This distance is called the detection distance. Younes analyzed the effect that sign size and sign material have on detection distance. Drivers were randomly assigned to one combination of sign size (small, medium, and large), and sign material (1, 2, and 3). Each driver covered the same stretch of highway at a constant speed during the same time of day, and the detection distance, in feet, was determined for the driver's assigned caution sign.

We present descriptions of designed experiments.

In each case, identify the

a. Experimental units.

b. Response variable.

c. Factor(s).

d. Levels of each factor.

e. Treatments.