A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Turn your working hypothesis into a claim
Planning your argument
Part I. Research and writing: from planning to production

We described the early stages of research as finding a question and imagining a tentative answer. We called that answer your working hypothesis. Now as we discuss building an argument to support that hypothesis, we change our terminology a last time. When you think you can write a report that backs up your hypothesis with good reasons and evidence, you'll present that hypothesis as your argument's claim. Your claim is the center of your argument, the point of your report (some teachers call it a thesis).