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37
votes
Accepted
How would you explain Moment Generating Function(MGF) in layman's terms?
For a continuous random variable, the raw $k$-th moment is by LOTUS:
\begin{align}\large \color{red}{\mathbb{E}\left[{X^k}\right]} &= \displaystyle\int_{-\infty}^{\infty}\color{blue}{X^k}\,\,\color{green …
14
votes
Accepted
Posterior Predictive Distribution as Expectation of Likelihood
$\newcommand{\y}{\mathbf y}$We have
$$
E_{\theta|\y}\left[f(\theta)\right] = \int f(\theta) p(\theta | \y)\,\text d\theta
$$
just by definition of expectation (and you could cite the LOTUS as well), and …
11
votes
Accepted
Variance of absolute value of a rv
The general calculation for both quantities can be obtained by the
application of LOTUS. …
11
votes
2
answers
10k
views
Expectation of square root of sum of independent squared uniform random variables
To apply LOTUS, I would need the pdf of $Y_n$. Of course the pdf of the sum of two independent random variables is the convolution of their pdfs. …
9
votes
Trying to approximate $E[f(X)]$ - Woflram Alpha gives $E[f(X)] \approx \frac{1}{\sqrt{3}}$ b...
Let us apply the Law of the Unconscious Statistician (LoTUS) to obtain :
\begin{align*}
\mathbb{E}[f(X)] &= \int_{-\infty}^{+\infty} e^{-x^2} \cdot \frac{1}{\sqrt{2\pi}} \exp\left(-\frac{x^2}{2}\right) …
9
votes
2
answers
3k
views
Computing variance from moment generating function of exponential distribution
X}\right] && \text{definition} \\
&= \int_{- \infty}^{\infty} x \cdot p_X(x) dx&& \text{just definition of expectation} \\
&= \int_{- \infty}^{\infty} e^{t x} \cdot \lambda e^{-\lambda x} dx&& \text{LOTUS …
7
votes
Accepted
Is downsampling a valid approach to compare regression results across groups with different ...
car_model %in% c('Lotus Europa', 'Ford Pantera L', 'Ferrari Dino', 'Maserati Bora', 'Volvo 142E'))
model = lm(mpg ~ disp * am, data = df)
summary(model)
#>
#> Call:
#> lm(formula = mpg ~ disp * am, data …
6
votes
Accepted
$Z=XY$, $E_Z[Z]$, $E_{X,Y}[XY]$
The LOTUS now involves two-dimensional real integrals, frequently expressed as Riemann or Lebesgue integrals. … .$$ LOTUS asserts this can be written as an "ordinary" integral, $$\mathbb{E}(Z) = \int_\Omega z\,p(z)dz.$$ The (bivariate) LOTUS, applied to $Z$ in in terms of $(X,Y)$, says this can be written $$\ …
6
votes
Accepted
Computing variance of squared difference of i.i.d. uniform random variables
1-y, & 0<y<1
\end{cases}$$
Here is the plot:
In this way,
$$\text{Var}\left[(U-U')^2\right]=\text{Var}[Y^2]= \mathbb E\left[Y^4\right]-\left[\mathbb E\left[Y^2\right]\right]^2\tag 1$$
Applying LOTUS …
5
votes
Accepted
Logistic Regression Trees in R
I wouldn't know of an R implementation of LOTUS. … The binaries for the original LOTUS implementation are available from Kin-Yee Chan's web page (http://www.stat.nus.edu.sg/~kinyee/lotus.html) but I think Wei-Yin Loh's recommendation nowadays is to use …
5
votes
Accepted
Is this MLE estimator unbiased?
You can do this directly using the distribution of the previous step and LOTUS or by first finding the distribution of $Z$.
Hint: the gamma family is a truly large family of distributions. …
5
votes
1
answer
1k
views
Logistic Regression Trees in R
Specifically, I am looking for a logistic regression tree implementation in R based on a specific algorithm (LOTUS - Logistic regression Tree with Unbiased Splits) developed by Kin-Yee Chan and Wei-Yin …
5
votes
1
answer
1k
views
Is this MLE estimator unbiased?
I worked it out and found how $\sum_i -\ln X_i = \sum Y_i \stackrel{\text{d}}{=} \Gamma(n,\theta)$ (through the hints supplied byJohnK), then I immedialty used LOTUS and found $E[\hat \theta] = \dfrac{ …
5
votes
1
answer
339
views
Finding mean and variance of $Y = \ln{\left(\sum_i X_{i}^{2}\right)}$ for $X_i \sim \mathrm{...
Im guessing for the mean we could use LOTUS such that
$$
\mathrm{E}[Y] = \int_{0}^{\infty}\dots \int_{0}^{\infty} \ln{\left(\sum_{i=1}^{n} X_{i}^{2}\right)} \prod_{i=1}^{n} P(X_i|\sigma) \; \mathrm{d}X …
4
votes
Accepted
Detailed proof of the Law of the unconscious statistician
cdots + g(99)P(X=99) + \cdots $$
which, if we are so inclined, we can recombine into gobbledygook involving $\displaystyle \sum$
by writing
$$E[Y] = E[g(X)] = \sum_i g(x_i)P(X=x_i)$$
which looks like LOTUS …