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Task 4 - Designing your experiment

This task is due for the third lesson.

This lesson may be too a good time to check the progression at work.

This task must be fulfilled before the next lesson.

Use your laboratory notebook to record the task.

Guillaume Paumier, Nicole Ebber, John Morrison -

Design experiment

Once you have formulated a hypothesis for your investigation, you must design a procedure to test it (really, you’re testing its predictions).

The first step of designing your experimental procedure involves planning how you will change your independent variable and how you will measure the impact that this change has on the dependent variable.

In your experiment, there are three types of variables to consider:

  • Independent variable: the one the investigator chooses to change.
  • Dependent variable: the one that is observed and recorded in the experiment for each and every change in the independent variable.
  • Controlled variables: variables that are kept the same each time.

Remember, in your experiment you need to make sure that the only thing you change is the independent variable. And, all the other variables must remain constant (controlled variables).

Adapted from: Science Buddies - Science Fair Projects - What are variables

Examples of variables for a hypothesis




How does the size of a dog affect how much food it eats?

Larger animals of the same species expend more energy than smaller animals of the same type. To get the energy their bodies need, the larger animals eat more food.

If I let a 70-pound dog and a 30-pound dog eat as much food as they want, then the 70-pound dog will eat more than the 30-pound dog.


(What I change)


(What I observe)


(What I keep the same)

Dog weight 

Weight of eaten food 

Space free of other foods

Type of food

Adapted from: Science Buddies - Science Fair Projects - Examples of Variables

Design experiment - Key info

Write the experimental procedure like a step-by-step recipe for your science experiment.

A good procedure is so detailed and complete that it lets someone else duplicate your experiment exactly!

Repeating a science experiment is an important step to verify that your results are consistent and not just an accident.

For a typical experiment, you should plan to repeat it at least three times (more is better).

If you are doing something like growing plants, then you should do the experiment on at least three plants in separate pots (that's the same as doing the experiment three times).

If you are doing an experiment that involves testing or surveying different groups, you won't need to repeat the experiment three times, but you will need to test or survey a sufficient number of participants to insure that your results are reliable.

Taken from: Science Buddies - Science Fair Projects - Experimental Procedure

Design experiment - Steps

Following the steps listed below will help you as you develop an investigative procedure:

1. Define variables

2. List materials

3. List steps

4. Estimate time

5. Check work

Adapted from: Science Fair Central - Scientific Projects - Steps