Final answer:
Brian is more likely to get a cold on days when there is a math test.
Step-by-step explanation:
From the given information, we can conclude that Brian is more likely to get a cold on days when there is a math test. This conclusion is based on the fact that Brian has gotten a cold on all of the last 10 days when there was a math test at school, but he didn't have colds at other times. It is important to note that this conclusion does not imply that Brian is allergic to math tests, only that there seems to be a correlation between math tests and colds for Brian.