# All Questions

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### Weights in cluster analysis in R

I have a data set of responses to a survey administered in three different locations. The number of responses from each of these, however, do not represent the underlying population of each area. I ...
0answers
4 views

### Most likely domain element in probabalistic forward model

Suppose I have some probablistic forward model $m: T \rightarrow U$, and that the model is then conditioned on observations $u_1, \dots, u_N$ from U. [More specifically, by 'probabalistic model' here,...
0answers
3 views

### Repeated-measure contingency table with two variables with many levels

I am trying to analyze the results of a survey on what would make people of different ages visit certain tourist places. However, age was collected as age-group (not my fault). Hence, it is a ...
0answers
17 views

### Consider tossing a coin 2 times, there are 4 possible sequences of outcomes, what is the name of each sequence, in the context of stochastic process?

In probability theory and related fields, a stochastic process is a mathematical object usually defined as a family of random variables. In probability and statistics, a Bernoulli process (named ...
1answer
7 views

### What is the difference between data perturbation and differential privacy?

I cannot distinguish the terms "data perturbation" and "differential privacy". If the data perturbation is the process that adds some small value sampled from specific distributions such as Laplacian ...
0answers
6 views

### How can I smooth data in 2D coordinates that has time-dependent error?

I have collected some GPS data from running over and around a hill many, many times. The hill itself is about 9-10 meters high compared to the ground around it, although when I collected data, my ...
1answer
11 views

### What is the relation between “conjugate priors” and the approximate inference?

I know that "conjugate prior" is to help us calculate the the denominator of the Bayes formula(to make the calculations easier). And I just learnt to approximate the inference by mean field ...
1answer
30 views

### Expectation of two $X \sim N(0, \sigma^2)$ $Y \sim N(0, \sigma^2)$

IF  $X \sim N(0, \sigma^2)$ $Y \sim N(0, \sigma^2)$  X and Y are independent => $X^2 \sim Gamma (\left(\frac{1}{2}\right), 2\sigma^2)$ $Y^2 \sim N(\left(\frac{1}{2}\right), 2\sigma^2)$ ...
1answer
3 views

### SSE not decreasing with increase in number of clusters

So as far as I know, SSE should decrease( or just never increases) as the number of clusters increases. I have an implementation of K-means where the parameter k was supplied as 5,10,15,20,25 and 30 ...
0answers
10 views

### 3 way ANOVA, residuals not normally distributed

It has been a while since I have learnt about more complex stats and I am utterly stuck, not even sure I am using the right test at this point. I am trying to perform a 3 way analysis of variance ...
0answers
10 views

### Figuring out GLMM family for S-shaped curve, or going non parametric?

I have two processes that output n-square matrices. I am interest in modelling these matrix norms as a dependent variable, according to the process used, and the matrix size n as predictors. I ...
0answers
12 views

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### Missing values in large spatial data

I have a groundwater dataset (4000 locations). For this data, the depth is very important to coordinate the data. I found that there are about 415 missing values in ...
0answers
12 views

### Problem on quadratic form [migrated]

Show that $\{x : x^{T}Ax \le 1\}$ is bounded if $A$ is positive definite, where $x^T=[x_1,x_2,...,x_n]$ and $A$ is an $n\times n$ matrix.
1answer
21 views

### Detrending time series for regression

I want to perform a regression between 3 variables [x1,x2,x3] that have no trend and no seasonality across their time observations and a variable [Y] that has trend and seasonality. For [Y] I've ...
0answers
16 views

### Keras predict probability too high

I've followed this tutorial to create a simple neural network that matches intents. The results are good and the process is relatively fast, however there's an issue with it. The probability is ...
0answers
26 views

### Ratio = 1 or Difference = 0

In two-sample testing, a standard way of examining for differences in variance is testing a null hypothesis that the ratio of two variances is 1. Let's set up the problem. Why not test that the ...
0answers
16 views

### One sample t-Test for proportional data

I have 4 group of fish (n=28 per group). I have measured the amount of time that a fish in each group spent exploring two different objects (A and B) in a squared shape tank. Then I have calculated ...
1answer
8 views

### Calculation of critical values

Are the critical values for the two-sample t-test with unequal variances calculated the same as for the two-sample z-test?
0answers
3 views

### Using ezANOVA or ezMixed

I am fairly new to R and have looked into other answers found on SE and SO but still do not feel that my case matches other posters' data. I would like to perform a Repeated Measures-ANCOVA on the ...
0answers
6 views

### How should I interpret irregular lag correlation in time series?

I'm not sure how to interpret the autocorrelation pattern I'm seeing in this time series and any help would be very appreciated. Below is the ACF plot for my data. To me this looks like seasonal ...
1answer
16 views

### How to represent gender or any non numerical data for a Logistic regression classifier?

I've coded a logistic regression classifier trained on the Kaggle Titanic dataset to predict whether or not a passenger will survive. I've noticed that depending on how I represent the gender the ...
0answers
11 views

### How to retrieve the data frame used in a GEE model fit? [migrated]

I have a longitudinal data frame with multiple rows per id. ...
1answer
37 views

### Which is the correct method for outlier analysis on a dataset for modelling?

I'm trying to build a regression model but my data-set have many outliers points which I need to analyze and then remove them. There are two ways to do it, 1) First do all the analysis on every ...
1answer
14 views

### How can I adress problems of heteroscedasticity in mixed model analysis?

I am analizing pupil size data using mixed model analysis in R. I use lme() from package nlme. However, I am encountering serious problems of heteroscedasticity and ...
0answers
5 views

### Variance Components of a Random-Intercept Covariance Matrix

My professor wants me to explain how the parameters of my model are estimated via penalized quasi likelihood. However, my understanding of (generalized linear) mixed models is still very basic and ...
0answers
4 views

### Path Model with (endogenous) Treatment - which model?

I have collected data on the intention to create a new business of my students. I measured it before the course (t1) and after it (t2). I have data on their absenteeism in class and the time they ...
0answers
15 views

### Estimate the time series like an event was never happened

I have data from a website where a specific advertising campaign happened a couple of years ago. What I want to do is to estimate how the signups on that website would have been without that big ...
0answers
8 views

### Simulated returns from copulas to use in portfolio allocation

I am currently trying to do some portfolio optimization by reproducing the methodology found in Sahamkhadam, Stephan & Östermark (2018) ("Portfolio optimization based on GARCH-EVT-Copula ...
0answers
5 views

### Is there a way to assess how much and in which direction a predictor is associated with class in my classifier?

I searched the forum, and couldn't find a matching question. I am building an MLP to predict an outcome (occurrence of a medical condition) in Weka. Previously I identified positive and negative ...
1answer
13 views

### What does $w_{ni}$ mean in the weighted nearest neighbour classifier?

Wiki gives this definition of KNN In pattern recognition, the k-nearest neighbors algorithm (k-NN) is a non-parametric method used for classification and regression. In both cases, the input ...
0answers
12 views

### How a softmax function can be used in multiclass classification?

I'm trying to understand how a softmax function help classify in multi-class classification. In Andrew Ng video, he shows how a simple 1 layer neural network, with 2 inputs ($x_1, x_2$) and 3 outputs ...
0answers
9 views

### ARIMA(0, 1, 0) or ARIMA(0, 0, 0) for Stock log-Returns Forecast

I'm trying to forecast the log-returns of Amazon's stocks using the ARIMA model, so I went through the traditional procedure of examining the autocorrelation plot and the partial autocorrelation plot ...
2answers
174 views

### Regression when x and y each have uncertainties

I have a set of $N$ points $(x_i,y_i)$. $X$ and $Y$ both have some noise associated with them due to measurement inaccuracy however the relationship of the underlying true values (i.e. if we could ...

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