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In a fair test only one factor or variable is changed everything else is kept the same. This way you can be sure that what you are measuring is the result of the changes you have made.

Independent and dependent variables

The condition that you change is called the independent variable. Everything else is kept the same. These are called the controlled variables. This means that any differences in the variable that you are measuring (called the dependent variable) can be attributed to the variable that you changed (the independent variable).

A fair test

In a fair test

keep everything the same except the one variable you are testing

minimise errors by careful measurement

use a control

repeat or replicate experiments .