Suppose we consider a large number of containers each containing initially 10000 atoms of a radioactive material with a half life of 1 year. After 1 year,
1
all the containers will have 5000 atoms of the material.
2
all the containers will contain the same number of atoms of the material but that number will only be approximately 5000.
3
the containers will in general have different numbers of the atoms of the material but their average will be close to 5000.
4
none of the containers can have more than 5000 atoms.