Top Tips !

Never write "amount" you mean mass, volume or concentration.
Refer to "a control experiment" or "a variable that I will control (and then name the value and method of control)" but never to "a control variable"
Independent variable is what you change.
Dependent variable is what you actually measure in the experiment (not rate).
Organisms vary from each other unless they are clones !
When you suggest improvements think about improving the method rather than the equipment (e.g. control a variable that wasn't previously)

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