Independent and Dependent Variables

“A student wants to find out if the amount of time spent studying affects test scores. They have some students study for 1 hour, some for 2 hours, and some for 3 hours before a test. What is the independent variable and what is the dependent variable in this experiment? A researcher is investigating whether different types of fertilizer affect the height of tomato plants. They give one group of plants Fertilizer A, another group Fertilizer B, and a third group no fertilizer. What is the independent variable and what is the dependent variable in this experiment? A company wants to determine if a new advertisement campaign increases sales of their product. They run the new campaign in one city and continue with their old campaign in another city. What is the independent variable and what is the dependent variable in this experiment?”