# All Questions

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### GAM model warning message: step failure in theta estimation

When running and gam model and this warning message pops up, what does this mean and what is advised? A simple increase in knots (even by 1) seems to remove this warning message. "Warning message:...
• 17
3 views

• 1,123
9 views

### GLS vs. OLS with sandwich (or GEE with sandwich?) - repeated data (no covariates!)

Let's assume I have a series of repeated observations at time t0..t3. I want to test the difference at each time point vs. t0. When doing a set of independent comparisons "vs. control" (...
5 views

### Sampling from a Poisson Process

I am trying to simulate a one dimension correlated random walk. In this algorithm, the direction of a particle’s next step is correlated with the direction of it’s previous step. The particle’s step ...
3 views

### Caret: ordinal models with VGAM library

I started to look into the students performance dataset: https://archive.ics.uci.edu/ml/datasets/Higher+Education+Students+Performance+Evaluation+Dataset I would like to train two models with caret ...
• 101
1 vote
15 views

### Can I convert a typical reinforcement learning problem to a supervised learning problem?

I'm not sure if I've understood correctly the whole point of reinforcement learning. In my point of view, the whole goal of RL is learning a policy that maps states to actions. Let us suppose that I ...
• 410
6 views

### The expected value of point product of matrices

I have two random binary matrices of the same size m*n. let's call them A, B I know r_i which is the row sums of A, and c_j which are the column sums of B what is the expected value of C_ij = A_ij*...
• 551
7 views

### Proper way to report on Confidence Intervals for 2 Proportions means

Disclaimer: Stat noob Context: I'm trying to figure out the best way to report CI to a non-data/stat/math savy audience. I'm performing a two proportion z test for an experiment. Control: 0.3097 ...
9 views

### forward stepwise AIC approach

I am learning about performing stepwise model selection by AIC and I have 2 questions here: 1.Regarding to stepwise AIC, what is contribution (effectiveness) of the number of parameters in the model ...
• 41
13 views

### Correlation of multivariate distributions without "slope"

Wikipedia has this image showing different correlations: It says: The correlation reflects the noisiness and direction of a linear relationship (top row), but not the slope of that relationship (...
• 547
27 views

### Why adjustment is needed when calculating Skewness and Kurtosis?

Some packages such as Mathlab, Minitab and SigmaXL caluclate adjustment for skewness and kurtosis. For example at: https://octave.org/doc/v4.0.1/Descriptive-Statistics.html it is suggested that ...
• 101
1 vote
9 views

### Fitted ARIMA on new time series

Based on the accepted answer from this post: How to use a fitted model parameters for forecasting other time series, it is possible to use a fitted ARIMA model for forecasting another time series. ...
• 81
14 views

### How does attention add expressive power to encoder-decoders?

I am learning about the attention mechanism for the first time, and the context in which it has been introduced (watching Lecture 8 of Stanford's CS224N) is that of language translation using seq2seq ...
7 views

### Summing confidence intervals, given $[a_0, a_1]$ and $[b_0,b_1]$, and $c=a+b$, is $[c_0, c_1]$ where $c_0 = a_0+b_0$?

How can you sum confidence intervals? Basically the title: Given $[a_0, a_1]$ and $[b_0,b_1]$, and $c=a+b$, is $[c_0, c_1]$ where $c_0 = a_0+b_0$? These are 95% CI's. How can you show this? Given ...
• 103
9 views

### Interpreting interaction effect with ln(time) in Cox regression

I am fitting a Cox proportional hazards model with the interaction effect dummy:ln(time). How would you interpret the result? Is it a simple exp(x)-1)*100 to receive the percentage increase in y? Coef:...
• 11
6 views

### Multilevel model for education data, if individuals within cluster change (school) between time points

If I am wanting to fit a multilevel model across two time points and the first time point is Primary (uk education system, age 7-11 - keystage 2) but the second time point is secondary education (uk - ...
• 115
14 views

### Multinomial Logistic Regression get predicted probabilities without using predict_proba()

I have a 5 class multinomial logistic regression using sklearn and I would like to achieve the same output as model.predict_prob() just using the coefficients and ...
• 11
8 views

### Multiclass classification on top of given probability distribution from previous model

I have a multiclass classification problem that has multiple steps. Firstly, I am given a probability distribution over the classes by a base model for each sample. The task is to create a new model ...
1 vote
21 views

### Building a bootstrapped distribution to test reliability of empirical data

I have data from a study where subjects (considered as "generations" in a Telephone-like game) sang short melodies from one to the next, starting from a randomly-generated melody (seed) ...
• 1,560
20 views

### Two Sample Independent Test for Proportions (z test or t test)

Context: I have two independent samples that I want to compare for equality through an AB test. The metric being evaluated is binary: user clicks or not (proportions). Question: I keep reading that z ...
55 views

### Linear regression's (OLS) coefficient interpretation with heteroscedasticity

To use OLS for inference, is it necessary in all cases that the premise of homoscedasticity is met? I need to check the influence of some features (eg age, income...) on a variable y (whether or not I ...
• 39
11 views

### Common Trend Assumption in Difference-in-differences

I'm running a DiD analysis on whether the introduction of a spinoff NFT (non-fungible token) collection affects the prices of the parent NFT collection. First thing that I did is to visually test ...
120 views

### How to assess normality under the OLS assumptions?

When we have a multivariate regression function, which assumption has to hold so that the OLS assumptions are not violated: ...
19 views

### Finding the non-zero region of a marginal

Basic question but: what happens to the region on which a pdf is non-zero when a bivariate is integrated to get a marginal? The example I'm working on (course problem booklet for a mathematics BSc ...
• 265
4 views

### Why does the IV estimator fail to attenuate the EIV bias in a two-stage FM regression?

In Jegadeesh et al. (2019), they proposed to use the instrumental variables (IVs) estimation approach to attenuate the errors-in-variables (EIV) bias, which is inherent to a two-stage Fama-MacBeth (FM,...
6 views

### How truncation works when applying BERT tokenizer on the batch of sentence pairs in HuggingFace? [closed]

Say, I have three sample sentences: ...
1 vote
14 views

### Neural networks - calculating output manually if $x_1=x_2=0$ . Should this be easy to do?

This is a problem question I'm trying to make sure I understand from a past paper (with no solutions). The R output is below. ...
4 views

### Interpreting Shapley Values on Breast Cancer

I was analyzing Shapley Values on the Wisconsin breast cancer data set (binary classification). I applied it on Random Forest and on Ridge and Lasso Regression. However the summary plot seems to be ...
• 1
5 views

### knitting rmarkdown throws error printing result of contour() [migrated]

I want to knit the following code into an html document. The code runs fine in Rstudio but fails when I attempt to knit - what am I missing here? ...
1 vote