Mmmm....don't know if this is valid

Okay, so the idea I gave before was a bit vague...and there was no real independent variable or dependent variable, and I've separated the experiment into two different experiments, so here goes:
How much water do you have to put into a cup to make sure that when it is inverted with a piece of paper covering the opening, the water doesn't fall out at all, even when your hand is removed?

Independent variable in this experiment: how much water you put into the cup.
Dependent variable: (without hand support) if the paper will fall off or not.
Controlled variables:

• Use same measuring cup for measuring amount of water, each time you measure
• Use the same cup for the water for repetition of experiment
• Use a flat piece of paper
• Make sure the paper is pressed firmly around the edges of cup so that it makes a fold on the paper around the edge of the cup
• make sure paper is not ripped
• use paper of the same thickness