4
$\begingroup$

Let $X$ be a random variable with real values and with density $f$. Assume the support $f$ is bounded with supremum $m$ and has a positive value at that supremum: $$\forall x > m, f(x) = 0 \text{ and } f(m)> 0.$$ Given an I.I.D. sample $X_1, \cdots, X_n$ of this random variable, I'd like to estimate both $m$ and $f(m)$. What would be an good way to proceed ?

I think estimating $m$ by the sample maximum $\max(X_1, \cdots, X_n)$ yields a consistent estimator of $m$ with rate $\frac{1}{n}$, which satisfies me.

But I'm not sure on how to estimate $f(m)$. I tried to count the number of sample points falling in the interval $$\left[ \max(X_1, \cdots, X_n) - \frac{S}{\sqrt{n}}, \max(X_1, \cdots, X_n) \right]$$ where $S$ is a consistent estimator of the standard deviation of $X$. Hoping this would give a $\frac{1}{\sqrt{n}}$ consistent estimator of $f(m)$, but this seems to converge very slowly, and I don't think this is the best option.

Any input on that question would be greatly appreciated.

$\endgroup$
4
  • $\begingroup$ How do you intend to distinguish between a case where the density falls rapidly to $0$ and one where it falls rapidly to a positive value, except with an enormous sample size? $\endgroup$
    – Henry
    Commented Oct 14, 2021 at 16:50
  • $\begingroup$ Sorry, I'm not sure I understood your comment. You mean what if the slope of the density is very negative at $m$ ? $\endgroup$
    – Pohoua
    Commented Oct 14, 2021 at 16:54
  • $\begingroup$ Does stats.stackexchange.com/questions/65866 answer your question? $\endgroup$
    – whuber
    Commented Oct 14, 2021 at 19:07
  • 1
    $\begingroup$ @whuber : Thanks for the link to this nice question and dicussion. I guess I could use the proposed technique by replacing 0 by the maximum of the data. However, the cutting/ reweighting, while giving a good estimate of the density, has a bias at the edge, which is the value I'm interested in. For the logspline density estimation, I couldn't find any guarantee that the estimation is pointwise consistent (which would be what I need). So I'm affraid this doesn't exactly answer my question. $\endgroup$
    – Pohoua
    Commented Oct 19, 2021 at 13:06

0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.