Unlike idea, test hypothesis is a detailed specification how to solve a problem we encounter on the website. In order for hypothesis to be sound, it must have a full definition of observed problem, an explanation why the problem exists and how to solve it.
Ideally, hypothesis should also include a quantified prediction or estimate of improvement once the proposed solution is implemented. Creating a hypothesis is absolutely necessary to start any sort of testing. If you do not have hypothesis than your test relies on pure luck. Hypotheses need to be ranked according to the level of importance or seriousness of the problem they need to solve, level of effort necessary to implement and test solution.
Hypothesis ranking is very important and there are several models we can use. By far the most comprehensive one we found is PXL, a framework developed by ConversionXL.