Ok, so you would use weight. Take the weight of the jellybeans divided by the weight of one jelly bean, to get a number of jelly beans.
1) Would the number of jelly beans that you calculated from this experiment be 100% guaranteed to be correct? Why or why not?
2) Why is this method better than simply randomly guessing a number between one and a trillion? Randomly guessing would also get a number of jelly beans.
Again, my two questions here were rather basic, and go directly to the point you are attempting to make about scientists' claims. If you could answer them, we can get to a very important idea, that we can both probably agree on.