6.13 Regression vs. Classification

  • Variables can be characterized as either quantitative or qualitative (= categorical)
  • Quantitative variables: Numerical values
    • Person’s age, height, or income,
  • Qualitative variables: Values in one of K different classes, or categories
    • a person’s gender (male or female)
  • Q: Are the following variables quantitative (A) or qualitative (B)?
      1. brand of product purchased, (2) wether a person defaults on a debt, (3) value of a house, (4) cancer diagnosis (Acute Myelogenous Leukemia, AcuteLymphoblastic Leukemia, or No Leukemia), (5) price of a stock
  • Problems with quantitative response = regression problems
  • Problems with qualitative response = classification problems
  • Distinction is not always crisp, e.g., logistic regression
    • Typically used with a qualitative (two-class, or binary) response
    • But estimates class probabilities
  • Source: James et al. (2013 Chap. 2.1.5)


James, Gareth, Daniela Witten, Trevor Hastie, and Robert Tibshirani. 2013. An Introduction to Statistical Learning: With Applications in R. Springer Texts in Statistics. Springer.