Hypothesis should state an expected relationship between two or more variables. Researcher should have definite reasons based on either theory or evidence for considering the hypothesis worthy of testing. Hypothesis should be testable. Hypothesis should be as brief as possible consistent with clarity. Null hypothesis is simply a statement that no difference will be found, and can be stated by rewording the hypothesis.
Hypotheses can be directional or non-directional.
Quantitative research generally requires that the hypothesis be stated at the beginning and prior to data collection. Qualitative research hypotheses are more likely to emerge during the research.