Traffic engineers are experimenting with two ideas. First is that erecting signs that say "Accident Reduction Project Area" along freeways will increase awareness and hence decrease accidents. Such signs may have the effect on traffic speed. Second idea is that metering flow of vehicles onto on-ramps will spread out entering traffic and lead to average increase in speed on freeway. Engineers perform the experiment to see how these two ideas influence average traffic speed.

First, twenty more-or-less equivalent freeway interchanges are selected spread well around the single metropolitan area and not too close to each other. Ten of these interchanges are selected at random to get "Accident Reduction Project Area" signs (in both directions); other ten receive no signs. Traffic lights are installed on all on-ramps to meter traffic. Traffic lights can be adjusted to need 3 or 6 seconds between entering vehicles. Average traffic speed 6:30-8:30 AM and 4:30-6:30 PM will be measured at each interchange on 3 consecutive Tuesdays, with our response being average of morning and evening speeds. At each interchange, three settings of traffic lights are allotted at random to three Tuesdays.

Examine the results using book's method and using more traditional split-plot method. Report conclusions. (Are they the same both ways?)