The problem statement is actually the question you are trying to answer with your experiment. It is written as a question. You must make sure it is testable. In other words, can you create and experiment to find your answer. Your problem statement sets up your investigation. Many problem statements start with the words "Which" or "How".
The wording of your problem statement is very important. It should be:
Which or How will the independent variable affect the dependent variable.
The project must be either a simple experiment in which you change something (manipulate a variable) and record the outcome without a control. Or it must be a controlled experiment which means that you will manipulate one variable in a group and compare it to a group that has no manipulated variable (control). Controlled experiments are more sophisticated than Simple experiments.
A hypothesis is an educated guess based on your research. It is a testable statement based on background knowledge, research, or scientific reason. Your hypothesis will state the anticipated cause and effect that may be observed during the investigation. When writing your hypothesis, always remember it must be written as an "If".... "then"... If (something is done) "then" (this is expected to happen).
If you follow the guidelines, your hypothesis can NOT be wrong. It will either be supported by the data, or it will Not be supported by the data. Do not change the hypothesis because the data does not support it. This is part of the way scientists think. They too learn from mistakes. The hypothesis is discussed in the conclusion and abstract.