Understanding the requirements of a scientific hypothesis is important if you have to compose one for a school science fair project or any other experiment. Hypotheses are basically educated guesses as to what will happen in a given situation. The scientific method entails finding a problem, coming up with a hypothesis regarding the solution to the problem and then testing that hypothesis to determine whether or not it is correct. The hypothesis is central to scientific investigation, and therefore a suitable hypothesis is needed for a good experiment.
The composition of a hypothesis is essentially a creative process, but it should be done based on existing knowledge of the subject matter. For example, if you were experimenting with ways to speed up a certain reaction, doing background reading on the relevant subjects is vital to composing a suitable hypothesis. If you didn’t know anything about chemistry, you may assume that extreme cold will speed up the reaction, when the reverse is actually true. Make an educated guess that provides a solution to the problem to compose a hypothesis.
One important requirement of a scientific hypothesis is that it is testable. The most common reason for coming up with a hypothesis is for use in a test, so an un-testable hypothesis is useless. For example, the hypothesis “Our universe has a parallel universe beside it that we can’t see or interact with” is possibly true, but unfortunately can never be tested. Whilst it may seem credible because it can’t be disproved, it is no more credible than any other unverifiable statement, such as “the moon’s orbit is controlled by an invisible dinosaur with imperceptible puppet strings.” For this reason, hypotheses must be testable.
Another requirement of a scientific hypothesis is that it can be proven incorrect. This may seem to be an extension of testability, but this is not the case. For example, the hypothesis “There is intelligent life on planets other than Earth” can be proven if one of the scientists listening to space for radio signals hears a broadcast in an alien language or if a space probe lands on a planet with intelligent life. Disproving this hypothesis is much more difficult, however, because even if there are no transmissions, and all the space probes we release find nothing, there could still be intelligent life on another planet. This hypothesis isn’t valid because it can’t be falsified.
Whilst not a requirement of a hypothesis, it is also important to think about how all-encompassing a hypothesis is. Most hypotheses can never really be proven; they can just appear more and more likely with each test. For example, the hypothesis “Any two objects dropped from the same height will hit the ground at the same time, as long as air resistance isn’t a factor” can be shown to be probably correct (as it was on the surface of the moon.) Despite this, two objects could be discovered tomorrow which behave differently, and thereby disprove the hypothesis. Despite this difficulty in truly proving things, reducing the scope of your hypothesis renders your results utterly meaningless. For example, saying “These two specific objects fall at the same rate without air resistance” doesn’t have any scope -- it only refers to two things. It is better to have a broad hypothesis that isn’t quite definitely proven than a narrow hypothesis that is conclusively true.