# All Questions

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2 views

### how to estimate hyper-parameters when cross-validating time series forecasting?

I want to evaluate several forecasting methods on the taylor time series using cross-validation. How do I go about selecting the hyper-parameters for the methods? ...
3 views

### Add Absolute Value as a Feature

In a machine learning context, does it make sense to have both a measurement and its absolute value transformation as features? There are already ~120 features in this predictive model (an elastic ...
2 views

### discriminator function in dual Generative adversarial network

I am reading the following article: https://arxiv.org/pdf/1803.00385.pdf On page 3 they explain how the losses for two discriminators (D1 and D2) is determined. D1 separates true upright image from ...
8 views

### Data set with known camera parameters

I am looking for a data set containing images of pedestrians/cyclists with static background and given camera calibration information (intrinsic and extrinsic) for a scene. I have already found EPFL ...
4 views

### ANOVA/Chi-square analog to GEE

If repeated measures anova is analogous to random-intercepts regression and regular anova is analogous to multiple linear regression because of the F-statistic. Is GEE logit or GEE poisson or ...
2 views

### Brown-Forsythe Test on Unbalanced Two-Way ANOVA

I am trying to create code in Matlab that runs a Brown-Forsythe test on an unbalanced two-way ANOVA. I am having difficulty figuring out the actual math behind this test and how to do it. I have read ...
8 views

### Translating the odds ratio

I have a question regarding a translation in odds ratio curve OR(x). More specifically, let's say we have an OR(x) which we get using logistic regression. We look at the interval bounded with 25% and ...
6 views

### Problem with non standard question about latent variable applied non-linear discrete choice models

Problem with non standard question about latent variable applied non-linear discrete choice models. I'm having issues because I couldn't find in the material I have in my possession any example ...
11 views

### Hypothesis testing - proportions

I'm curious about the procedure on how to execute a hypothesis test for following hypotheses on a 10% significance level: How do I calculate the test variable? For which levels of Z do I reject ...
10 views

### Do we use confusion matrix for Gradient discent

I would like to use two algorithms then evaluate their result both of them are based on logistic regresion based on gradient discent the second model contains aditional features I would like to ...
7 views

### Back-calculation of the minimum sample size for an mechanical experiment [on hold]

I want to back-calculate the minimum sample size for an experiment. I have a known mean and standard variance of a statistical population. From the statistical population I chose two samples with ...
7 views

### Is it possible to train an RNN to predict projectile motion?

Projectile motion is given by a function $y = -9.81 x^2 + ax + b$ for some parameters $a$ and $b$. I'll simply assume for $x$ values to be distanced by 1, so $x_t = t$. I can then easily generate ...
9 views

### Direction of a one sample Wilcoxon signed rank test

I am comparing a selection of values which come from a non-normal distribution to 0. I've done a wilcoxon in python: result = scipy.stats.wilcoxon(values) my W ...
9 views

### l2 lambdas in Keras.regularizers

Is the value supplied to the shrinkage regularizers (l1 and l2) in Keras the inverse of the lambda coefficient? e.g. ...
12 views

### What is the relationship between estimation error, approximation error, bias, variance in machine learning?

I'm a beginner in machine learning. I was reading http://ciml.info/ 5.9 Bias/Variance Trade-off According to this book: The trade-off between estimation error and approximation error is often called ...
4 views

### What is the meaning of non-nested model in Vuong's test in R?

I am having hard time understanding the use of nested and non-nested models. According to Ben-Akiva's description the nested models are blue bus/red bus problems, where the choice set has multi ...
4 views

### Determining weights for fitting non-uniformly spaced measured data

I have a system of generally known behavior, and some non-uniform measurements of that behavior (let's say without measurement error). Now I want to fit a simple function to a subset of the ...
14 views

### Shrinkage priors

I am building a Bayesian model where I to put shrinkage priors such as spike and slab, horseshoe prior, etc on some parameters for feature selection, but I am not able to decide which one is the best. ...
18 views

### Mann-Whitney U & Wicoxon W

I ran the Mann-Whitney in SPSS. In addition to the U, the output generated the Wilcoxon W and the Z score. Why would the W and Z be present in the output? I cannot explain them being present. Also, ...
8 views

### Lagged independent variable's coefficient changes when higher lags are included

I am running a model with which I want to explain students' performances. I lagged my main independent variable by two years. Now, my results show a negative coefficient for the two years lagged ...
8 views

### How to compare two PCAs

I am working on a deep learning research and came across the following problem: I have a network (let's call it A) that performs a certain task with X% ...
29 views

### Use of expression “statistically significantly positive”

Suppose one estimates a linear model $$y=\beta_0+\beta_1 x+\varepsilon$$ and finds that $\hat\beta_1>0$ and the $p$-value associated with $\hat\beta_1$ is lower than the chosen significance ...
16 views

### Lasso regression doesn't converge

I wrote this very simple python code: X = np.array([[1,0], [0, 1]]) Y = np.array([0, 0]) clf = sklearn.linear_model.Lasso() clf.fit(X, Y) then I got the ...
26 views

### Mean of predicted values in a log-linear model

I run a log linear model $$\log(Y)=\alpha + \beta X + \epsilon$$ and wonder how to calculate the mean of predicted values, in the same dimension as the initial (untransformed) variable Y. I would ...
10 views

### Confusion on Hypothesis Testing [on hold]

I don't know when to use Type 1 or Type 2 error when given a question. For example, if given data and told to test if there is a significant regression of Y on X and also calculate the correlation ...
28 views

### Interpreting the results of Chi-Square test

I have the following data: ...
11 views

### What is an example to show Wald's test does not confirm significance at the same level for each variable?

Suppose that the true model is given by Y=0.3+X1+X2+X3. Assume we have 100 training examples where each covariate vector (X1, X2, X3) is randomly drawn from some distribution P and Y is generated ...
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### What are the statistical methods to reduce a large data set to a specific ratio? [on hold]

I have a data set of about 10,000 rows, 6 columns "First Name", "Last Name", "Gender", "Age", "Marital Status", "Occupation" I want to reduce the data set to 350 by these selection criteria; ...
6 views

### Measure Similarity by Considering Magnitude [on hold]

Is there any measure in the literature that allows measurement of similarity between two variables by considering their magnitude? For example, variable ‘a’ and ‘b’ both take values in range [0,1]. ...
12 views

### Optimal lag-selection in VAR-model in R

Having troubles with the lag specification of a VAR-model. The purpose of the model is to measure orthogonal impulse/response function of oil price shocks on macroeconomic variables, such as GDP-...
8 views

### How should I proceed to classify images of not ok microchips

So I have a new project where I have to classify different types of damages on microchips. I am new to machine learning and python in general so I am a little bit lost. I have over 100.000 images I ...
17 views

### Can I use LASSO as a variable selector with only three variable?

Can we still use LASSO even when we have a small number of variables?
13 views

### Applying logistic regression with response and expected response

I hope my title is phrased correctly, otherwise feel free to rephrase it. This is my first time working with such a data set and i'm trying to understand if a method i'm using is correct. Here is a ...
16 views

### How many experiments to run (sample-size) if I know I am going to feed them to a non-parametric regression?

I have 2 input variables, $X_1$ and $X_2$ that affect output variable $Y$. I can run experiments where I modify the inputs and measure what happens to the output. Now, if $X_1$ and $X_2$ were binary, ...
10 views

### Finding a varying code into a text

I'm rather new to Machine Learning but I have been looking into it for a bit now. Specially I've been interested in text classifying solutions and seen how a high level of success has been achieved in ...
9 views

### Is it necessarily incorrect to randomize train-test split for a time series random forest model?

As part of some preliminary research, I'm experimenting with a random forest classification model for predicting whether the S&P 500 will be higher or lower at tomorrow's close versus today's ...
8 views

### Alternative to plug-in estimation for log-tranformed linear model

I want to estimate a relationship of the form: $$y=ax^b\times\epsilon$$ If I log this model i get: $$\log(y)=\log(a)+b\log(x)+ \log(\epsilon)$$ If I then proceed and estimate this model using a ...
9 views

### Dempster Schafer theory [on hold]

can anybody clarify that how dempster Schafer theory works how to calculate the mass and bel in this theory? suggest me any solved example to get some knowledge related to this. R&D on this theory ...
4 views

### CDF for a vector-Matlab [on hold]

I have an equation with 2 variables, x and y. x and y are random variables. The question is: Ln(Z)=aLn(x)+bLn(y)+c a,b and c are constant and already determined. I need to calculate CDF of Ln(Z). I ...
48 views

### Why do we use the Greek letter μ (Mu) to denote population mean or expected value in probability and statistics

According to this Wikipedia entry, "Mu was derived from the Egyptian hieroglyphic symbol for water, which had been simplified by the Phoenicians and named after their word for water". So, my question ...
4 views

### Significance of initialisation of Kernel in sklearn.gaussian_process.kernels

I have been going through Gaussian Processes. In one of the code I stumbled upon there is this statement, I am not quite sure of the parameters that are passed to initialise it. Please help me. ...
17 views

### How does BATS model work?

I am using BATS on a univariate time series model. I have observed strange behaviour. I have data from 2016 to till date (weekly level). If actual are considered from 2016 to 2019 May, I have used ...
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### Does endogeneity problem matter when proving the existence of association/causality relationship?

In social science field (particularly Finance and Operations Management), we usually need to prove or disprove hypotheses of the type: X are positively associated with Y. One of the typical method to ...
17 views

### How to do a comparison between A or B between ten samples

I am planning a research which will go as follows, There will be ten participants and each will perform the same exercise. However they will be wearing the variant A or variant B of the garment we ...
5 views

### Different results with different functions for competing risk regression with Fine-Gray model

I am doing competing risk regression. I have three possible functions and one of them produces completely different results than other two. In my dataset I have time to event, status (censored=0, ...
7 views

### Measure for in equality of prediction quality in mutlclass classification

I have got a balanced dataset of 10 different classes $y\in\{0,\dots 9\}$. After fitting a ML model I get classification results $y^*$. Despite the data being balanced, the results are not. I want a ...
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### Probability that output is result of the same process?

I've developed a simple Monte-Carlo simulation. Output of this simulation is a histogram. This histogram is possibly a log-normal distribution, but I don't want to assume that. But I do know that the ...
3 views

### error in runing SOM

I am trying to run a SOM for my both qualitative data in five-levels (1-5) and quantitative data for 23 variables. unfortunately, I got this error SOM set.seed(222) g <- somgrid(xdim = 4, ...
14 views

### Interpretation of zero-one-inflated beta models in brms

I have 20 participants who have watched 18 clips. Every clip belongs to one category of pleasure (p_cat: negative, neutral, positive) and one category of intensity (i_cat: low, medium, high). I have 2 ...
6 views

### RNN (LSTM) training on multiple time series

Regarding RNN training, We feed network a network -> point by point from the same time series (or image or smth else). When we “switch from one time series to another”, what should be done or how ...

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