Since science does not claim to know everything, inference is behind all science, except in those few cases where everything is known about a whole population. It is important to note, also, that inference underlies most thinking, even the unscientific type. In this way, scientific inference is not unlike common sense. What distinguishes scientific inference is that the process is made explicit and follows certain rules, which are the subjects of this lecture. Hypothesizing usually begins after one has examined the existing knowledge base, reviewed the relevancy of theories, and understood something of the context within which the phenomenon of interest occurs.
Research questions are longer and broader than hypotheses.
A good hypothesis implies all these forms in a single sentence, and the trick is to express them as briefly as possible and in simple English. All theories contain hypotheses, but you sometimes have to read them into the theories. There's no need to elaborate all hypotheses capable of being generated by every aspect of a theory, but a single theory can generate many hypotheses with its twists and turns. Extant knowledge is what you obtain from a literature review. Sampling goes to the heart of inference because a sample is what one draws on to test hypotheses and make generalizations.