Gravity

We know about gravity and how everything comes back down..... but do they come down at the same time when they are different sizes ????
To test this we  had 3 different balls that we let go from the same height at the same time and tried to see which landed first  or if they all landed at the same time. We repeated the experiment 5 times because scientists always test and retest. Our results kept changing so we need to think of ways to make this test more fair .