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Comparative testing and fair testing

Comparative testing and fair testing are very similar. Both require you to control variables in order to help answer questions. And both require you to make comparisons between different materials or objects.

Whilst there may not be a clear distinction between the two it is generally agreed that fair test investigations are more scientific and should be carried out with older children (7-11 years). Fair test investigation require children to observe and measure the effect changing one variable has on another whilst keeping all other variables the same.

In a comparative test children will have less control over the variables. For example which tissues are best at soaking up water? Children can control most of the variables; the volume of water and size of tissue. They cannot control the thickness or the design of the tissue. This test would simply identify which tissue was best at soaking up water. The children would not be able to identify the variable/characteristic that was responsible for making the tissue the best at soaking up water.


5-7 year olds may use a comparative test to investigate which material would make the best umbrella. Children would compare no more than 3 or 4 different materials in this type of investigation. The children would be able to say which material was best and may even begin to suggest what properties make materials suitable for a specific purpose.

10 -11 year olds could carry out a fair test to investigation to find out the safest coloured clothes to wear at night. Do bright clothes make you more visible? Do black clothes make you invisible?

By placing different coloured fabric under a lamp children could measure the amount of light reflected using a data logger. To make this a fair test the children would have to keep the light the same distance from the fabric, use the same type, size and thickness of fabric and measure the reflected light from the same distance from the fabric.

Can you think of any questions that could be answered using a comparative or fair test?

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This article is from the free online course:

Teaching Primary Science: Getting Started

National STEM Learning Centre