Correlation and linear regression

Read correlation with the scatter · Diagrams

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Eight scatter patterns

Read shape, direction and scatter

Compare the patterns below.

Linear relationship

6 points

Linear relationship. Inspect the shape as well as the direction.

Curved: inverted U

9 points

Curved: inverted U. Inspect the shape as well as the direction.

Curved: loop

8 points

Curved: loop. Inspect the shape as well as the direction.

Positive linear

5 points

Positive linear. Inspect the shape as well as the direction.

Negative linear

5 points

Negative linear. Inspect the shape as well as the direction.

Strong negative linear

4 points

Strong negative linear. Inspect the shape as well as the direction.

Strong positive linear

6 points

Strong positive linear. Inspect the shape as well as the direction.

Weak/no clear linear

13 points

Weak/no clear linear. Inspect the shape as well as the direction.

Schematic illustrations: positions are not measured observations. No numerical data or calculated correlation is implied.
Look for shape before describing direction or strength.
A clear curved relationship can have little or no linear correlation.

Eight schematic panels, retaining source point counts: positive line 6 points, inverted-U curve 9, loop 8, positive line 5, negative line 5, strong negative 4, strong positive 6, and weak/no clear linear cloud 13. A curved or loop relationship can be strong without being linear. Positions illustrate patterns, not measured data.

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