Variability
Variability tells you how scores differ from one another.
For example
----------------------
Group A has scores of 3,3,3,3,3
Group B has scores of 2,3,3,4,3
Group C has scores of 6,4,2,2,1
All groups have a mean of 3.
But which group has more variability within it?
If you guessed C, you are correct!!
So while knowing the mean is useful, knowing variability adds knowledge about the group.
For example
----------------------
Group A has scores of 3,3,3,3,3
Group B has scores of 2,3,3,4,3
Group C has scores of 6,4,2,2,1
All groups have a mean of 3.
But which group has more variability within it?
If you guessed C, you are correct!!
So while knowing the mean is useful, knowing variability adds knowledge about the group.