How an investigator determines how to change the independent variable?

Question

i am confused on this question the way it is worded? anyway here is what i think.. i am not sure if i even answered the question but could somebody please review what i have written down bellow and give me suggestions to better what i have. or even a website.

The independent variable deliberately varies throughout the experiment. Scientist are only limited to one independent variable throughout the entire experiment. He/she measures the dependent variable to learn the effect of changing the independent variable.

This is not a good explanation could anyone give me a better more reasonable explanation. thank you:)

Answer 1

Dependent variables and independent variables refer to values that change in relationship to each other. The dependent variables are those that are observed to change in response to the independent variables. The independent variables are those that are deliberately manipulated to invoke a change in the dependent variables. In short, "if x is given, then y occurs", where x represents the independent variables and y represents the dependent variables.

Eg. The affect of pH on enzyme activity. The experimenter decides on the pH values to use (the independent variable) and then measures the enzyme (the dependent variable) activity.