MEPX
Chapter 8 of 10All chapters
  1. 1What statistics is for
  2. 2Averages
  3. 3Spread
  4. 4Distributions
  5. 5Sampling
  6. 6Confidence and error
  7. 7Testing a claim
  8. 8Relationships between variables
  9. 9How statistics mislead
  10. 10Doing it well

Chapter 8 of 10

Relationships between variables

Correlation and regression.

Correlation

A correlation runs from -1 to 1 and measures how tightly two variables follow a straight line. A strong curved relationship can score near zero.

  • Plot the data: identical statistics can hide completely different shapes.
  • Correlation says nothing about which caused which, or whether either did.

Regression

A regression line predicts one variable from another and quantifies the relationship. Extrapolating beyond the range of the data is where it stops being evidence.