Spread

Standard deviation

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Spread matters as much as the centre.
• Standard deviation $\sigma$ = square root of the average squared distance from the mean.
• Shifting all values moves the mean but not σ. Scaling all values scales both.

Steps

1. Same average, different story
2. Standard deviation
3. Compute σ
4. Scaling the data
5. A z-score
6. Add a constant