what are independent and dependent variables? which one do we modify during an experiment?
The independent variable is the variable that is manipulated during an experiment, and it gets its name because it is independent of other factors. It's the cause of the experiment that changes the dependent variable, which is the variable that is affected during an experiment.
In contrast to this, the dependent variable is the variable that is affected during an experiment. In our experiment, our dependent variable would be plant growth since this is affected by the amount of fertilizer applied. If you think of the independent variable as the cause, then the dependent variable is the effect. If the independent variable is not the only factor that could affect the dependent variable, then you would have to make this factor a control variable. This is a variable that is controlled during and between experiments. In our fertilizer experiment, we would control for the amount of sunlight received by each plant.