Is empiricism necessarily rational?

Empiricism is typically associated with rationalism. The two are almost used interchangeably at times. But, empiricism is a method in which conclusions are drawn based only on the evidence of the senses. This always involves a process of interpretation in which the sense data are interpreted. However, what if you were just crazy? What if you assiduously observed sense data but came to wrong conclusions anyway? Does that mean you weren't being empirical?