A dependent variable is the number of colonies produced. The experiment gives a useful insight into the toxicity of the chemicals.
A scientific experiment must always have a dependent and an independent variable. A dependent variable is the variable whose outcome is being determined by manipulating the independent variable which in this case is the presence or absence of the chemicals.
Toxicity of chemical substances is a very important information to scientists as such this experiment is very important because it highlights the toxicity of the chemicals to living things.
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