What is controlled experiment?

Answer 1

A controlled experiment is one in which only one variable is changed at a time. A variable is something which can vary, or have different values. Scientific investigations always involve three types of variables: 1) The independent variable: this is the variable which you deliberately alter, so you will know its values before you start the experiment. For example, if you want to know how the amount of light a plant gets affects its growth, you must give aome plants different amounts of light. Since you need to choose the amounts, you will know the values of this variable before you start the experiment. 2) The dependentvariable:this is the variable you must measure to find out if it changes as a result of you changing the independent variable. Since you have to measure it to find out its values, you will not know the values (ie the results) before doing the experiment. In the plant example you wouls have to find some way of measuring plant growth in the different light conditions. 3) Controlvariables: these are any other variables which may affect the values of your dependent variable, so they need to be kept constant to make it a fair test. In our example, things like the temperature or the amount of water could also alter plant growth, so they would have to be kept constant. These variables are also called confounding variables. The basic principle is only alter one variable (the independent variable) at a time; keep everything else the same. See: http://www.sciencebuddies.org/science-fair-projects/project_experiment_fair_test.shtml http://www.fair.science-resources.org/sci_meth.htm

Answer 2

A controlled experiment is something that helps you control your experiment.