Final answer:
In the study measuring car pollution from gasoline with different lead amounts, the amount of lead in the gasoline is the independent variable and the pollution output is the dependent variable.
Step-by-step explanation:
The independent variable in the scenario where the amount of pollution produced by cars is measured for cars using gasoline containing different amounts of lead is the amount of lead in the gasoline. The independent variable (IV) is the factor that's being manipulated or changed in an experiment, and in this case, it's the varying lead content. On the other hand, the dependent variable is the amount of pollution produced by cars, as this is the outcome that researchers are measuring in response to the changes in the independent variable.
To illustrate another example, when considering a scatter plot of weight versus fuel efficiency, the weight of the vehicle would be considered the independent variable since it is the factor being manipulated and the fuel efficiency would be the dependent variable since it is the aspect being measured and likely to change in response to the vehicle's' weight.