A bus company wanted to know if the number of complaints they received was a function of the number of buses it ran. The company carried out a study comparing the average number of buses per hour for different days and the number of complaints that it received on those days. Here are the results: Number of complaints Avg. number of buses per hour All of the scatter plots below display the data correctly, but which one of them displays the data best? By convention, a good scatter plot uses a reasonable scale on both axes and puts the explanatory variable on the -axis.