What is a Fair Test in Science?

A fair test is a test that controls all but one variable when attempting to answer a scientific question. Only changing one variable allows the person conducting the test to know that no other variable has affected the results.

To help remember how to conduct your fair test, learn the mnemonic:

  • Cows – Change one thing (independent variable)
  • Moo – Measure something (dependent variable)
  • Softly – Keep everything else the same (controlled variable)

As students progress through their academic careers, even more importance will be placed on carrying out fair tests. Marks are set aside to provide evidence of an appropriate test in their experiments, particularly on Year 7 and Year 8 science tests. When conducting a science assessment in class, ask your students to consider the variables – what variable are they manipulating to change the result? What variables must not change for the results to be most accurate?
It can vary wildly between experiments, so it is essential that your class is comfortable with conducting their investigations and can identify variables accordingly.

Example of a Fair Test

Let’s look at an example of a simple experiment that could be conducted with a primary class.

  • Build a ramp out of four books and a plank of wood.
  • Roll a tennis ball down the ramp and measure how far it travels.
  • Next, roll a ping pong ball down the ramp and measure how far that travels.
  • Compare the results of the two tests and discuss why the differences might have occurred.

This simple test covers all of the bases for a fair examination. Our independent variable is the type of ball used. The dependent variable is how far the ball moves, and the controlled variables are the height of the ramp and the material used to make the ramp.

Why is it essential to do a fair test?

When conducting a scientific experiment, the experiment must be a fair test because if the test is not acceptable, then the results will not be accurate, which will reduce the test’s effectiveness by making the results incorrect.

When conducting experiments, scientists will always ensure that the test is fair; they do this to ensure that no other variables affect the test results, and this ensures that the test results are as accurate as possible.

When gathering the results of an experiment, the same method must be used to measure the results of each test to ensure that it is fair. Scientists will also do multiple repeats of the experiment to ensure no mistakes or unknown factors change the outcome of the investigation.

When children ask what is a fair test in science, the essential part of the answer should be that it is a test in which only one variable is changed, and the results are measured using the same method each time to ensure that the results are correct.

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