A hypothesis is an assumption, or set of assumptions, made on the basis of limited evidence that either:
a) asserts something as a starting point for further investigation; or
b) confirms something as highly probable in light of established facts.
For a hypothesis to be a scientific hypothesis, it is required that one can test it. A working hypothesis is a provisionally accepted hypothesis proposed for further research.
For the purposes of medicines development, the interest is in the hypothesis that asserts something – for example that a new treatment for a disease is better than the existing standard of care treatment.