An urn has n balls and we take balls from it with replacement until each ball has been drawn at least one. X denotes the number of draws required. What is the expected value and variance of X? I think X is at least n, is it true? And how should I find the expected value of it?

  • 1
    $\begingroup$ This is known as the coupon collector problem, $\endgroup$ – lulu Nov 12 '18 at 15:29
  • $\begingroup$ Thank you so much $\endgroup$ – werlless Nov 12 '18 at 15:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.