A civil engineer is testing the reliability of traffic signal controllers produced by two different companies. He has 20 sets of controllers from each company, and he has been given clearance to install them at 40 different intersections in the city. He randomly assigns the controllers from company A to 20 intersections and the controllers from company B to the other intersections. The most important reason for this random assignment is that: a. randomization is a good way to create two groups of 20 intersections that are as similar as possible, so that comparisons can be made between the two groups.
b. randomization eliminates the impact of any confounding variables.
c. randomization makes the results less variable.
d. randomization ensures that the study is double-blind.
e. randomization reduces the impact of outliers.