Formative assessment probes are used not only to uncover the ideas students bring to their learning, they can also be used to reveal teachers' common misconceptions. Consider a process widely used in inquiry science--developing hypotheses. In this article, the author features the probe "Is It a Hypothesis?", which serves as an example of how formative assessment probes can also be used for teacher learning. After answering the probe and examining the explanation, one may experience some cognitive dissonance that will lead to changing one's conception of "hypothesis" and more important, changing how one conveys this critical term and skill to students. This is transformative learning--learning that leads to fundamental changes in deeply held beliefs or misconceptions. This probe is designed for middle, high school, and college students. (Contains 1 figure and 1 online resource.)