Variables

Independent variable- the variable in an experiment that you control; the one that you change and manipulate to find a different outcome

Dependent variable- the outcome of changing the independent variable in an experiment; "depends on the independent variable"

Controlled variable- something that is constant and unchanged in an experiment.

Being sure you have all of these variables in your experiment will ensure its validity.
•Without a controlled variable, you wouldn't have anything to compare the new product too
•Without an independent variable, you wouldn't have anything for your dependent variable to rely on for your conclusion
•Without a dependent variable, you wouldn't have an experiment because your dependent variable is what your comparing

You should do multiple trials in an experiment to be sure it's accurate. You never know if maybe there was a mishap in the first try, or there was a miscalculation in the third. People make mistakes, even scientists. All you can do for an experiment is to continue your trials over again to be sure you didn't have a brain fart.