Now, Alex wants to do a second experiment to see how the amount of liquid changes in the same 2 cups (1 with the old lid, 1 with the new lid) over time.
She decides to leave them out for a month. She designs the following procedure:
1)Fill each plastic cup with liquid and put the lid on the cup.
2) Draw a line where the liquid level is on each cup.
3) At the end of 30 days, weigh the 2 cups to see if there is a difference in mass between them.
If Alex wants to use the liquid level as her dependent variable, what steps did Alex miss to get the data she would need to use the liquid level as her dependent variable?
(If Alex wants the liquid level to be her dependent variable she should ____________________)