Time to create your hypothesis test. You have picked your Hypothesis and now it’s time to test it! Often times this part of the science fair experiment is the most fun. You get to perform a test to see if what you thought would happen does in fact happen.
The first thing you will want to do is to make a list of supplies you will need in order to do your hypothesis test. You may want to talk to your parents or teachers in order to determine where you can acquire what you need. (Most materials can be had from home improvement centers or hobby shops.)
Try to be specific when you are making your list in order to make the rest of the project go smoothly. For instance: if you think you need a battery for your science fair experiment, make sure to specify exactly what kind of batter you will need – 9 volt? 1.5 volt? A watch battery? Your shopping will be easier if you know exactly what you are looking for and your report will look better if you specify exactly what you used.
When you think you have listed everything you need, close your eyes and envision your project. Think about everything that is supposed to happen during your experiment from start to finish.
Do you have a way to write down or otherwise record what is going on during the experiment? If you need batteries, do you need more than one? What if one runs out of power during your experiment? If you need a liquid solution of some kind, how much will you need?
What if you want to run your experiment more than once (you should!) in order to verify your results? Be sure to have everything that you will need on hand; otherwise you could be spending valuable time going back to the store to get more supplies instead of finishing your experimentation.
To do a hypothesis test for our tomato plant example we would need a container to hold the experiment, two vessels – one for the nutrient solution and one for the potting soil – we would then need to fill each vessel with the appropriate growing medium, plant the seeds, and place lighting (or put in a lit area.) We might also have a camera on hand to take pictures on a daily basis to document growth. We may want to have measuring sticks next to our plants in order to better (more accurately) note size differences. And so forth.
Once you have everything you need, setup your science fair experiment for testing according to what your question and hypothesis was.
Your science fair experiment may not involve growing anything – your hypothesis test may take a few seconds, a few minutes, or a few days. After you setup your experiment you are going to run the experiment by enacting your Independent Variable and then measuring your Dependent Variables. In our tomato plant case, our Independent Variable was the growth medium (nutrient solution vs. potting soil) and our Dependent Variables are the growth differences between our plants.
Before you run your experiment, make sure that you:
When you have all of these things taken care of, there is one last thing to do: Run the experiment! Since you have a list of exactly what steps to take to do this, all you have to do is follow your own instructions.
Ok, once you have run your science fair experiment you should have some information (data) about your hypothesis test.
Did your Dependent Variables behave the way you expected? Did they mostly behave the way you expected? Note anything that you did not expect. Once you have done this, run your experiment again (if you can) and record those new results.
Compare your results: are they about the same? If they are, chances are that you have done your science fair experiment correctly! If not, try to figure out if there is a Controlled Variable that you have not accounted for messing up your experiment. If you find one - don't worry - simply adjust your experiment to take that new variable into account.
Your science fair experiment is not invalid if your hypothesis proves to be false because of your hypothesis tests! Believe it or not, the most important aspect of your experiment is how well you follow the scientific method when doing your experiment!
A somewhat mathematically dense explanation of a hypothesis test can be had at wikipedia.
Just because your hypothesis did not pan out does not mean your experiment is without merit – quite the opposite. Some of the best science experiments show how a seemingly obvious hypothesis turns out to be incorrect when critically tested by correctly using the scientific method.
Now that you have done your experimental runs, it's time to move on.