Questions tagged [mathematical-statistics]
Mathematical theory of statistics, concerned with formal definitions and general results.
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8 views
Help with interpreting contrasts in statistics
I've been stumped by this question for days now. I find contrasts a little bit difficult to understand and I definitely do not know how to interpret the contrast and turn it into words.
Is anyone ...
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0answers
15 views
How to show that R2 is a function of \hat{\beta}_1
Given \Y_i = \beta_0 + \beta_1 \X_i + \u_i.
How do we prove the following that R2 is a function of \hat{\beta}_1.
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1answer
20 views
Calculating variance of process with time-varying variance
This is a question stemming off a previous post I had regarding calculating portfolio volatility.
For a portfolio consisting of multiple assets, I understand that there are multiple ways to calculate ...
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0answers
14 views
Population mean, median, and mode for the normal distribution [on hold]
In many text books note that the population mean, median, mode are equal. Why it be like that? So when we need to construct the variable follows the standard normal distribution, could it be (x.bar - ...
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1answer
29 views
Calculating portfolio volatility from portfolio returns vs. from covariance matrix
I'm having trouble understanding the difference in calculating portfolio volatility via the portfolio returns vs. via the covariance matrix.
To be more specific: I understand that on the individual ...
-3
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1answer
27 views
Statistics and Probability. Please show solution [on hold]
Miss Romero noted that the mean scores of a random sample of 15 grade 8 students who had taken a special test were 80.5. If the standard deviation of the scores was 3.1 and the sample came from an ...
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0answers
18 views
Log Likelihood and parameter space
I'm taking a 3rd year statistical theory class in which we're introducing the likelihood function with a bit more mathematical rigor.
Under the discussion for maximizing the likelihood function $\...
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0answers
7 views
Specifying the bandwidth parameter for Local Whittle estimation
In every Local Whittle function I have seen I have to set bandwith parameter usually denoted m such that
m = floor(1+T^delta).
I am interested in the delta, how do I choose what value to put in the ...
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0answers
28 views
How to compare two dispersion measures in a specific probability density function?
I am very interested in the properties of a specific probability density function (pdf) proposed in this article.
It seems to me that this pdf is a very general one to capture the properties of wide ...
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1answer
21 views
How to modify the mean and variance/dispersion of a given distribution
I am trying to find a parametric adjustment that allows modifying the mean and variance/dispersion of a given distribution.
Ideally, this adjustment would be implemented through a parametric function ...
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0answers
36 views
Variance of permutation test p-value?
The one-sided p-value for permutation testing is $ \tilde{p} = (r + 1)/(n + 1)$, where $n$ is the number of permutations and $r$ is the number of p-values that are equal to or greater than the p-value ...
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0answers
36 views
Fitting 2D data [on hold]
I have a 2D data-set. If we plot, it looks like the image below (to some extent):
This distribution mostly follow a Gaussian shape with some mismatch. For the sake of simplicity let's assume it a ...
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0answers
14 views
Please Help Me Identify And Solve This Question [on hold]
The following are average weakly losses of worker-hours due to accidents in 10 industrial plants before and after a certain safety program was put in operation :
Before: 45 73 46 124 33 57 83 34 26 ...
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0answers
7 views
Dependency of variable P on multiple factors, and factors interactions
In my data, I have a variable/vector P which is dependent on variables X, Y, Z, K and gender. The factors X, Y, Z are interacting.
What kind of statistical tool/method I can use to explore dependency ...
1
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1answer
39 views
Algorithm for modified knapsack problem
We have n-players in a game. We have a population of players we can choose from. Each player score is a normally distributed random variable and each player has a cost to add to the team. We are ...
3
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1answer
39 views
Are the law of iterated expectation and the law of total expectations the same?
On the Wikipedia page of the Law of total expectations it is said that
The proposition in probability theory known as the law of total expectation, the law of iterated expectations, the tower rule, ...
2
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1answer
35 views
Accounting Student taking Master in Stat, need your help regarding taking subjects
I had a Bachelor in Accounting and now I'm doing a Masters in Statistics.
This is my first semester and I have to Choose at least 3 out of 6 offered subjects for this semester. These subjects Are:
...
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0answers
41 views
Is the uniform distribution stationary? [on hold]
Is the uniform distribution stationary or non-stationary?
The normal distribution is stationary in all cases?
The normal distribution is non-stationary in which cases? or in all cases else normal?
-...
2
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1answer
19 views
AR(1) Finding $\gamma_l$
I have $\gamma_l = Cov(r_t, r_{t-l})$ as a definition in my notes and now I need to find $gamma_l$ for a series $r_t- m = p(r_{t-1} - m) + a_t$ where $r_t$ is a linear time series with expected value $...
2
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2answers
29 views
OLS with ARMA errors, tip or two
I need a tip or two.
I am performing OLS with dynamic factors (4x1 factors each representing a PANEL of 24 series, hence 4 time series).
My OLS has autocorrelation in the error so I want to use OLS ...
2
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0answers
15 views
Principle coordinates analysis - visualization and assigning text to graph in r [closed]
I've recently run a principle coordinates analysis in r with ~ 200 subjects and 17 binary variables. I've plotted my points successfully, the challenge I'm facing is that when I plot the text with the ...
1
vote
1answer
35 views
Use linear projection without constant to obtain the linear projection with constant
We know that the linear projection of $y$ on $x_0$ $x_1$, $x_2$, . . . $x_K$ always exists and is unique:
$$L(y|x)= \gamma_0 x_0 + \gamma_1 x_1 + ... + \gamma_k x_k = x\gamma$$
where $x = (x_0, x_1, ...
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0answers
18 views
In a manuscript, is an incomplete beta function a useful simplification of a sum, if the argument ends up negative?
I'm working on a manuscript which I intend to submit to a statistics journal. I have a sum which I "simplify" to the regularized incomplete beta function $I_{-t}(a,b)$, where $t$ is a positive real ...
1
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0answers
9 views
Distribution of a square of a random variable [duplicate]
If X is normally distributed with mean mu and variance sigma^2, then what can I know about the distribution of X^2 ?
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0answers
12 views
Structural models and relationship (statistical associations)
I'm starting to study econometrics from the Wooldrige's book. But some doubts arise regarding the structural model, its definition and its comprehension in general. Let's look at the author's opinion. ...
1
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0answers
21 views
Linear Regression Expected Value [duplicate]
Whiles reading An Introduction To Statistical Learning under linear regression (Chapter 3), I found:
$$E(Y - \hat{Y})^2 = |f(X) - \hat{f}(X)|^2 + Var(ε)$$
where $E(Y - \hat{Y})^2$ represents the ...
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2answers
80 views
Is $(1-L)Y_t=\epsilon_t \to Y_t=(1-L)^{-1} \epsilon_t$ mathematically correct?
Consider an AR(1) model with coefficient $\rho =1$, i.e. a random walk, $Y_t=Y_{t-1}+\epsilon_t$. We usually say that since the AR polynomial has a unit root, it cannot be inverted and therefore the ...
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0answers
25 views
Help needed making Random Permutations in R studio [migrated]
I am very new to R and struggling a bit with getting my head around things.
I need to make random permutations out of my data set, I have 5 categories (these are age classes) 10, 16, 21, 26, 36. ...
2
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1answer
25 views
Using a generalised linear model for tennis winning probability
I have a dataset of historical tennis matches, one row per match. Each row has the ELO points of each player, and a calculated ELO difference. And of course a column to indicate if Player 1 won as a 1 ...
1
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0answers
9 views
Stationarity of ADL(p, q) with heteroskedasticity
Suppose I have the model
$$y_t = \alpha_0 + \alpha_1 y_{t-1} + ... + \alpha_p y_{t-p} + \beta_0 x_t + ... + \beta_q x_{t-q} + \epsilon_t,$$ where $\{x_t\}$ is a stationary process and $\epsilon_t$ has ...
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0answers
7 views
Identification of mixture models with location shift
I am studying identification of mixture models of the type
$$
F(x)=\sum_{j=1}^J \lambda_j G(x-\mu_j)
$$
with $F,G$ denoting univariate CDFs, $G$ symmetric about $0$, $\mu_1<\mu_2<...<\mu_J$, $...
1
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1answer
37 views
Proof for simulation of NHPP by thinning
Background:
I'm trying to show equivalency between the density function for a non-homogenous exponential process (NHEP?), (i.e. the arrival times of events generated by a non-homogenous Poisson ...
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0answers
29 views
proof related to gamma distribution function [closed]
Finding gamma distribution from the given probability distribution function as shown in this picture.
A random variable x is said to be gamma-distributed with index α if its probability density ...
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0answers
7 views
Marketing Funnel Percentage Calculations
I implement a marketing funnel in python and I have an issue around the topic that I can't solve neither in statistical level.
Lets say that we have the funnel A which contains
...
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0answers
11 views
Given a simple logit panel data model, the MLE estimators are inconsistent
Consider a binary choice model, $P \left( y _ { i t } = 1 | x _ { i t } , \alpha _ { i } \right) = F \left( x _ { i t } \beta _ { 0 } + \alpha _ { i } \right)$, $$F ( z ) = \frac { e ^ { z } } { 1 + e ...
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0answers
14 views
How are cumulants of order higher than one independent of average? [closed]
I have background in physics. How are cumulants of order higher than one independent of average?
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1answer
16 views
Sample size needed?
I need some help calculating the minimum sample size needed for my upcoming trial. I’m doing higher degree research on eHealth, so I have little knowledge about statistics and sample size calculation. ...
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0answers
26 views
What is the relationship between Online Learning and Statistical Learning?
Online Learning also known as Online Convex Opimization has famous algorithms like Follow-the-Leader and Online Gradient Descent (See OCO Book)
Now stoastic programming has algorithms like Sample ...
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0answers
23 views
Reconstruct full Observations of a Time serie
I'm working on a project concerning a prediction of full observations applied to wind data (a time serie) which is called "Statistical Downscaling".
From a time serie X which covers 20 years for ...
4
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0answers
32 views
Uniform distribution on the simplex. - Thomas cover
I'm trying to formulate the solution for the following problem:
I was thinking in finding the equivalent distribution on $X_i$ based on $Y_i$, but I think I'm cheating. I think that the autor wants ...
1
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1answer
25 views
What happends if we standarise with a slightly shifted mean?
For deep neural networks or any ML algorithms , lets say the mean of my dataset is 5 and instead I normalize with 6 or 4, something slightly off. What affect does this have on learning?
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0answers
11 views
Using GARCH to model seasonal variance clustering
Question: is it a good idea to model variance clustering in a time series with GARCH when the clusters are seasonal?
Details: Imagine that we are given a time series $(x_t)_{t\in \mathbb{N}}$ that ...
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0answers
13 views
In the superpopulation framework of causal inference, what is the necessity of assuming the outcomes, treatment and covariates are jointly iid?
In the textbook "Causal Inference for Statistics" by Rubin and Imbens, the following argument is made on pg. 39:
"In part of this text we view our sample of size N as a random sample
from an ...
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1answer
51 views
How to Identify dependent variable from my dataset?
I have a dataset which consists of 50 variables. I want to programmatically(using python) identify what is my dependent variable is. Are there any tests to separate the dependent variable from ...
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0answers
10 views
Help with centered multiple linear models
For the multiple linear model in centered form
prove that
where is the L-2 norm, defined as
Any help would be greatly appreciated. Perhaps links to papers, chapters, websites that could help me ...
3
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1answer
24 views
Algebra in Cantelli-Cheybyshev Inequality Proof
I am confused by the following (possibly simple) algebra in the proof of the Cantelli-Cheybyshev inequality. I am following Rohatgi and Saleh (2015, Section 3.4 Lemma 1) where we plug in $\phi(x)=(x+c)...
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1answer
18 views
Get better confidence interval by drawing multiple samples
Imagine that I have population of size N and I draw a sample of size n from which I compute a proportion $\hat{p}$ of a categorical variable.
And I want to get a confidence interval of 95%. So I ...
1
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1answer
17 views
relationship between correlation, covariiance and conditional distribution
What are the relationships between correlation and conditional distribution. For instance, given three dependent variables, X1, X2 and ...
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0answers
12 views
Statistical significance regression analysis [duplicate]
Imagine a regression with 3 independent variables. All variables have positive and statistically significant signs. When you add other variable, the coefficient of your main interest variable becomes ...
0
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1answer
33 views
