You conduct a quasi-experiment to assess the impact of raising the speed limit from 55 to 65 miles per hour. You find that there are more accidents in the 6-month period following the speed limit change than in the 6-month period before the speed limit change. Although it is tempting to say that raising the speed limit caused higher accident rates, you must be careful because O you have an adequate understanding of the operational definition of an "accident" O you don't have an independent variable in this design. O there is no problem with drawing this causal conclusion O other variables (for example, cheaper gasoline or the season of the year during which the change was instituted) may also be affecting accident rates