When planning an investigation, the first stage is to come up with a hypothesis. Many students see a hypothesis as prediction of the outcome of an experiment - but it is a lot more than that. This GCSE Biology quiz will help you get to grips with what exactly a hypothesis is.
A hypothesis is a prediction backed up with a scientific reason saying why you think the prediction is correct. Effectively it is what you expect the outcome of an experiment to be and the reason why you expect it. The experimental part of your investigation is then aimed at testing your hypothesis. Always keep reminding yourself of your hypothesis when planning your experiment as that will help to keep you on track.
An example of a hypothesis would be that 'seedlings growing in a greenhouse will grow faster than seedlings on a window sill because there is more light for photosynthesis'. To improve on this, you could add 'there is more light because it is coming into the greenhouse from all sides and not just from the side where there is the window'.
Variables will affect the outcome of your experiment so they need to be identified. Once you have your hypothesis, you can then begin to identify the independent variable, the dependent variable and the control variables. The dependent variable is the factor that you think will change. In the example above, the dependent variable is therefore the growth rate. The independent variable is the factor that you think will cause the dependent variable to change, in our example it would be the amount of light. The control variables are harder to work out and you may find that you add more control variables to the list when you are designing your experiment. The more detail you add to your hypothesis the more it will help you to make sure that the experiment you design will investigate the right variables. It helps you to control the variables better too.