In a MythBusters episode, the was asked, 'Which is better? A four-way stop or a roundabout?' 'Better' was determined based on determining the number of vehicles that travel through the four-way stop over a 5-minute interval of time. Suppose the folks at MythBusters conducted this experiment 15 times for each intersection design. What is the variable of interest in this study? Is it qualitative or quantitative?