Variation exists in every measurable aspect of life, from weather to the stock exchange to sports results. It provides the topics for much of our casual conversation.
- It's 22 degrees now but it was only 3 degrees this morning.
- The stock exchange has been fluctuating wildly around 4000 points.
- How could my team win by 24 points last week and lose by 37 this week?
Variation is fundamental and directly connected to the other four big ideas.
- Expectation grows naturally out of variation (i.e. what is typical) but decisions about expectation must acknowledge underlying variation.
- Visual representation of variation is so critical that distribution demands attention.
- Variation in data is often the result of randomness; informal inference seeks to explain it.
There is further information on the fundamental ideas of variation and expectation in the article Inference as Prediction on the AAMT website.