Math 2.0

Probability theory and stochastic processes Inequalities Theorem

Hoeffding's inequality

Builds on Independence of random variablesExpected valueChernoff bound

Statement

Let X1,…,XnX_1, \dots, X_n be independent real random variables with ai≤Xi≤bia_i \le X_i \le b_i almost surely, where ai<bia_i < b_i are reals. Let Sn=X1+⋯+XnS_n = X_1 + \dots + X_n. Then for each t>0t > 0, P(Sn−E[Sn]≥t)≤exp⁡(−2t2∑i=1n(bi−ai)2).P\left(S_n - E[S_n] \ge t\right) \le \exp\left(-\frac{2t^2}{\sum_{i=1}^n (b_i - a_i)^2}\right).

Remarks

The same bound holds for P(Sn−E[Sn]≤−t)P(S_n - E[S_n] \le -t). So P(∣Sn−E[Sn]∣≥t)≤2exp⁡(−2t2/∑i(bi−ai)2)P(|S_n - E[S_n]| \ge t) \le 2 \exp\left(-2t^2 / \sum_i (b_i - a_i)^2\right). The proof uses the Chernoff bound together with Hoeffding's lemma: E[es(X−E[X])]≤es2(b−a)2/8E[e^{s(X - E[X])}] \le e^{s^2 (b - a)^2 / 8} if a≤X≤ba \le X \le b. For nn independent tosses of a coin with P(heads)=pP(\text{heads}) = p, the fraction HH of heads satisfies P(∣H−p∣≥ε)≤2e−2nε2P(|H - p| \ge \varepsilon) \le 2 e^{-2n\varepsilon^2}.

History

The inequality is named after Wassily Hoeffding.

Reading path

To understand this page from the ground up, read these 60 pages in order. The foundations come first.

  1. Construction of the reals from Cauchy sequences concept
  2. Element definition
  3. Integers object
  4. Ordered field definition
  5. Proposition concept
  6. Random experiment concept
  7. Rational numbers object
  8. Real numbers object
  9. Set definition
  10. Ring of integers statement
  11. Disjunction definition
  12. Implication definition
  13. Predicate definition
  14. Ordered pair definition
  15. Union definition
  16. Sample space definition
  17. The rationals form a field statement
  18. Existential quantifier definition
  19. Universal quantifier definition
  20. Cartesian product definition
  21. Subset definition
  22. The rationals form an ordered field statement
  23. Uniqueness quantifier definition
  24. Binary relation definition
  25. Universal set definition
  26. Order on the reals definition
  27. Power set definition
  28. Complement definition
  29. Function definition
  30. Interval definition
  31. Injective function definition
  32. Preimage of a set definition
  33. Sigma-algebra definition
  34. Countable set definition
  35. Event definition
  36. Borel sigma-algebra definition
  37. Probability axioms concept
  38. Probability measure definition
  39. Probability distribution definition
  40. Probability space definition
  41. Conditional probability definition
  42. Monotonicity of probability statement
  43. Random variable definition
  44. Independence of two events definition
  45. Cumulative distribution function definition
  46. Discrete random variable definition
  47. Law of a random variable definition
  48. Random variable with a density definition
  49. Mutual independence of events definition
  50. Probability mass function definition
  51. Expected value definition
  52. Probability density function definition
  53. Independent sigma-algebras definition
  54. Markov's inequality statement
  55. Law of the unconscious statistician statement
  56. Independence of random variables definition
  57. Moment definition
  58. Moment-generating function definition
  59. Chernoff bound statement
  60. Hoeffding's inequality statement

Where this leads

2 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Hoeffding's_inequality, Statement
About this page
Tag0WPDNXGSSN
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Kindstatement, theorem
WritingW0 stub
MSC60E15
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UsesIndependence of random variables, Expected value, Chernoff bound
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