What are the two types of hypotheses used in a hypothesis test? How are they related?
A research hypothesis and a 'null-hypothesis'
A research hypothesis is, basically, an educated guess as to what is believed will occur during an experiment. It is what the experimenters are attempting to 'prove'.
A null-hypothesis is a statement which is the opposite of the research hypothesis. That is to say, it generally postulates that there is no link between the outcome of the experiment and the variables being changed during the experiment.
Researchers (should!) refer to their null hypothesis when concluding their research and state whether they have been able to disprove it or not.