Machine-translated by Google. Questions are authored in English.
Top

Discussion

Suppose \(\{X_{n}, n \ge 1\}\) is a sequence of independent and identically distributed random variables each following uniform U(2, 6) distribution. Which of the following is not true ?

  • A.\(X_{(n)}\) converges to 6 in probability
  • B.\(X_{(1)}\) converges to 2 in probability
  • C.\(X_{(n)}\) converges in law to exponential distribution
  • D.\(M_{n}\) converges in probability to 4, where \(M_{n}\) is the median of \(\{X_{1}, X_{2}, \ldots, X_{n}\}\)

Answer: C

The false statement is that \(X_{(n)}\) converges in law to an exponential distribution.

For U(2, 6), \(P(X_{(n)} \le 6 - \epsilon) = \left(\frac{4 - \epsilon}{4}\right)^{n} \to 0\), so the maximum converges in probability to 6, and hence in law to the degenerate distribution at 6, not to an exponential. Likewise \(X_{(1)} \to 2\) in probability, and the sample median converges in probability to the population median 4.

An exponential limit appears only after rescaling: \(n(6 - X_{(n)})\) converges in law to an exponential distribution with mean 4. Without the factor \(n\) the limit is a point mass. So the first, second and fourth statements are true and the third is the one that is not.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.