Final answer:
Mrs. Cai's class was more successful because her interquartile range (IQR) was less spread out.
Step-by-step explanation:
In order to determine the class that has had greater success on field day over the last 10 years, we need to analyze the box plots. The best evidence to show this is that Mrs. Cai's class was more successful because her interquartile range (IQR) was less spread out.
The IQR measures the spread of the middle 50 percent of the data, so a smaller IQR indicates less variability in scores. This suggests that Mrs. Cai's class had more consistent performance on field day compared to Mr. Roland's class or any other class.