Skip to content

Expected largest value and spread of n uniforms

Question

Draw nn independent random numbers, each uniform on [0,1][0,1]. What is the expected value of the largest one? What is the expected difference between the largest and the smallest?

Short answer

nn+1\tfrac{n}{n+1} and n−1n+1\tfrac{n-1}{n+1}. The maximum has CDF xnx^n, so E[max⁡]=∫01(1−xn) dx=nn+1\mathbb{E}[\max]=\int_0^1(1-x^n)\,dx=\tfrac{n}{n+1}. By symmetry E[min⁡]=1n+1\mathbb{E}[\min]=\tfrac1{n+1}, and the expected range is the difference.

Adapted from Joshi, Denson & Downes, Quant Job Interview Questions and Answers, Q3.29, p.83; question and answer rewritten by SelfMadeQuant.com.

See the hint and the full worked solution in the question bank (free account).

Open the worked solution

Lessons behind this question

Start with a free lesson: Expectation, Variance and Covariance is part of a free topic. Create a free account, no card needed, to read it in full with worked solutions.

Read it free