A hypothesis is a statement of presupposition. Some hypothesis might suggest that one thing causes another while some might suggest that there is a relationship between two variables. A statement of hypothesis must be based on a priori assumptions (i.e based on theoretical presuppositions). It means that the statement must be accompanied with some testable propositions that will either nullify or confirm the hypothesis. It is not a hypothetical assumption, if a statement suggests that one thing causes another or there is an association between A and B based on a posteriori assumption. Assumption is what you think that most people accepted to be the truth about the issue. Example, daily, people make assumptions without knowing. For example, a week ago, a friend of mine, an African student at the Lund University was in my office when his mobile phone rang. The call was from his brother back home. After hearing that his sick uncle had died responded:
1- The man would not have died if he had money to receive medical treatment.
2- In a later conversation with me, he added, most of the premature death in developing countries are caused by poverty.
In 1 & 2 statements, he made hypothetical statements without knowing. The two statements suggest that the death of the uncle and premature deaths in the developing countries are positively associated with lack of money. The two statements will remain hypothetical assumptions until proven by testing some hypotheses. Therefore, an assumption is untested claim of reality while hypothesis is a construct that would be tested to determine the validity of the presupposition.