Jensen’s Inequality

Statement

Given a convex function 𝑓 and a random variable 𝑋, then:

  • 𝑓(𝐄[𝑋]) ≤ 𝐄[𝑓(𝑋)]

as the number of samples of 𝑋 approaches infinity

Visualization

When 𝑓 is a Straight Line

When 𝑓 is a Convex Function

  • 𝑓(𝐄[𝑋]) = 𝐄[𝑓(𝑋)]

  • 𝑓(𝐄[𝑋]) < 𝐄[𝑓(𝑋)]

Resources