Variation

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.