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Moments are summaries of random variables' characteristics (e.g., location, scale). Use also for fractional moments.

1 vote

Variance of sample moments - clarification on Serfling (1980)

In general, for $k,\ell$ moments, set $i=k-1, j=\ell-1$ in the variance-covariance expression. …
Alecos Papadopoulos's user avatar
3 votes
Accepted

Joint raw moments of multivariate normal

To close this one, as whuber's comment pointed out, let a multivariate distribution be symmetric in the sense $$(X_1, \ldots, X_m) \sim_d (-X_1, \ldots, -X_m)$$ Suppose also that moments exist. …
Alecos Papadopoulos's user avatar
1 vote

If $\mathbb{E}|X_n|=O(a_n)$, how large is $Y_n = X_n\ln\left(\frac{1}{X_n}\right)$?

Since $X_n$ are positive random variables, we do not need the absolute value. We have $$\{\mathbb{E}X_n\}=O(a_n) \implies \lim_{n\to \infty}\frac{\mathbb{E}X_n}{a_n} < K \in \mathbb R_{++}$$ Then, s …
Alecos Papadopoulos's user avatar
6 votes

What is the difference between the parameters and the moments of a distribution?

The moments of a distribution are defined as expected values of specific functions of the random variable following this distribution. Raw moments $\mu'_k \equiv E(X^k)$. … Central moments: $\mu_k \equiv E[X- E(X)]^k$. Fundamentally $k$ is taken to be an integer, but there is also theory developed for fractional moments (i.e. with $k$ not being an integer). …
Alecos Papadopoulos's user avatar
6 votes

Econometrics text claims that convergence in distribution implies convergence in moments

Indeed, it is a known erratum of this book (see its website in the errata .pdf), that the specific lemma does not state the moment-boundedness condition $$\exists \; \delta : E(|z_n|^{s+\delta}) < M …
Alecos Papadopoulos's user avatar
1 vote
Accepted

Strictly Stationary Time Series with Infinite Moments

Both are strictly stationary processes, the first has the "infinite/undefined moments" issue, while for the Logistic process, the moments exist. … These are more primitive concepts than the moments. So for example if the moments do not exist, this does not mean that the concept of "location" is also undefined. …
Alecos Papadopoulos's user avatar
5 votes
Accepted

Asymptotic distribution for moments of gaussian distribution

As given in A. Dasgupta (2008) Asymptotic Theory of Statistics and Probability, ch 3, p. 42, The reference to Serfling is Serfling R.J. (1980) Approximation Theorems of Mathematical Statistics.
Alecos Papadopoulos's user avatar
7 votes
Accepted

Definition of sample excess kurtosis?

The Wikipedia equation uses the biased, maximum likelihood estimator for the sample variance (divide by $n$), while, as you say the function from the R-packages uses the bias-corrected formula (divide …
Alecos Papadopoulos's user avatar