I've tried and can't figure it out!!!! help please!!

In any set of data, there is a possibility that a score will be an outlier - an extreme score - that is not truly representative of the underlying variable being measured. Consider your first four tests this term to constitute a group of scores measuring you statistical knowledge. Some may feel that one of your test grades is an outlier. Using the statistics we've learned, generate a statistical argument for the exclusion of an outlier in from your data set. Convince me based on the statistical analysis of the data and your explanation of the results of the appropriate statistics that a low test grade represents such an outlier.

I know how to carry out the tests, im just not sure which test to do!!! the information i have is my 4 test scores and if its relevant (im not sure it is), the class avg. if someone can please help? thank you!