Scatter Diagram
Linear Correlation — Chapter 2, GSEB Class 12 Statistics
What is a Scatter Diagram?
A scatter diagram (or scatter plot) is a graphical method of studying the relationship between two variables. One variable is plotted on the horizontal axis (X) and the other on the vertical axis (Y). Each pair of observations is plotted as a dot. The pattern of dots reveals the type and strength of correlation.
Scatter diagram is a visual judgment method — no calculation is needed. It gives a quick first impression of the relationship before computing r.
5 Patterns of Scatter
Click each pattern to see how the dots arrange themselves:
Perfect Positive
r = +1All dots lie exactly on an upward-sloping straight line. r = +1.
| Pattern | Dot Alignment | Direction | r Value |
|---|---|---|---|
| Perfect +ve | Straight line ↑ | Upward | +1 |
| Perfect −ve | Straight line ↓ | Downward | −1 |
| Partial +ve | Band sloping up | Upward | 0 to +1 |
| Partial −ve | Band sloping down | Downward | −1 to 0 |
| None | Random cloud | — | ≈ 0 |
Key Takeaways
Key Takeaways
- A scatter diagram plots pairs of observations as dots on an X-Y graph.
- Perfect positive: all dots on an upward line (r = +1).
- Perfect negative: all dots on a downward line (r = −1).
- Partial positive/negative: dots form a band, not a perfect line.
- No correlation: dots scattered randomly with no pattern (r ≈ 0).
- Scatter diagram is a visual judgment tool — no calculation needed.