It can have as many as it needs. You can even change different variables at the same time and study their individual influence with proper statistical tools in many type of experiments.
Any amount can be changed as long as one stays the same
A controlled experiment has at least two factors or variables: the independent and the dependent. The independent variable is the factor against which all dependent variables are tested.
All experiments are set up to test one factor at a time.
There are three types of variables tested: manipulated variables, controlled variables, and experimental variables.
1
In a properly designed experiment, it is important to have at least 2 controlled variables. With two variables you are able to remove one at a time and see the effect in your setup.
An experiment of any kind can have infinitely many variables. A controlled experiment can have just as many, provided that all but one are kept exactly the same.
2
There are three types of variables tested: manipulated variables, controlled variables, and experimental variables.
1
In a properly designed experiment, it is important to have at least 2 controlled variables. With two variables you are able to remove one at a time and see the effect in your setup.
An experiment of any kind can have infinitely many variables. A controlled experiment can have just as many, provided that all but one are kept exactly the same.
2
It depends on the experiment. Normally only one is tested at a time because they can affect the experiment. Variables are tested in a controlled experiment to see whether they affect the outcome and also how.
to gather data from data to create an controlled experiment
to gather data from data to create an controlled experiment
to gather data from data to create an controlled experiment
to gather data from data to create an controlled experiment
In a controlled experiment only 1 variable is being tested.
1