What is the hypothesis? Hypothesis (plural hypothesis) is a suggested explanation of observation. Definition depends on the subject. For example, in science, hypothesis is part of the scientific method. This is a prediction or explanation tested by experiments. Observations and experiments may overturn scientific assumptions, but they can never fully prove a hypothesis. However, in the study of logic, the hypothesis is an if-then proposition, usually written as “if X, then Y”. In common usage, the assumption is only a proposed explanation or prediction, which can be tested or not. Most scientific hypotheses are presented in if-then format, because it is easy to design an experiment to test whether there is a causal relationship between independent variables and dependent variables. This hypothesis is written as a prediction of experimental results. Zero Hypothesis and Substitution. Statistically, it is easier to show that there is no relationship between two variables than to support their connection. Therefore, scientists often put forward zero hypothesis. The null hypothesis assumes that the change of independent variables has no effect on dependent variables. In contrast, alternative assumptions indicate that changing an independent variable has an impact on a dependent variable. Designing an experiment to test this hypothesis can be tricky because there are many ways to state an optional hypothesis. Consider, for example, the possible relationship between a good night’s sleep and good grades. Zero hypothesis can be used to say, “Sleep time has nothing to do with student performance” or “Sleep time has nothing to do with student performance”. An experiment to test this hypothesis may involve collecting data, recording the average sleep time of each student, and Gr Adams’hypothesis that students who sleep eight hours usually perform better than those who sleep four hours or ten hours may be rejected. But another hypothesis is more difficult to put forward and test. The most common saying is, “The amount of sleep students get affects their grades.” This hypothesis can also be described as “If you sleep more, your grades will improve” or “Students who sleep nine hours do better than those who sleep more or less.” You can collect the same data, but statistical analysis is unlikely to give a high confidence limit. Usually, scientists start with zero hypothesis. Therefore, it is possible to propose and test alternative hypotheses in order to narrow the relationship between variables.