# All Questions

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### In reinforcement learning, after an action, the state does not change

After conducting an action, the state of the agent may change into a new state, also may not change. So is it still reasonable to formulate the problem by MDP and solved it by reinforcement learning ...
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### Causal inference - difference between blocking a backdoor path and adding a variable to regression

I have just started this introductory course to causal inference. The DAG approach is completely new to me even though I come from an econometric background (though that dates back to 15 years ago). ...
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### How to properly calculate the average across multiple correlations?

I'm trying to obtain an average across 3 correlations. Using Python, I obtain these correlations with: corr = df.apply(lambda s: df.corrwith(s)) which outputs: <...
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### Merging survival data with time varying covariates

In merging the data in R the censored observations are merged well but the observed subjects are not. For example, the second subject had an event at time 0.546. How can I merge the time varying ...
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### How to explain these jump-discontinuities in the expected stopping time of a SPRT?

Suppose a sequential probability ratio test (SPRT) with $$\alpha=P(\text{Type I error})=P(\text{Type II error})=\beta = 10\%$$ is used to decide between $$\ H_0: p=1/2\quad\text{vs.}\quad H_1: p=b\,$$ ...
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### causal graph - counting the number of backdoor paths in a DAG

I am following "A Crash Course in Causality: Inferring Causal Effects from Observational Data" on Coursera. I am struggling at correctly identifying backdoor paths in causal graphs (or DAG ...
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### Example of time series with constant variance+expected values but time-dependent covariance

I just started to learn about time series analysis and I want to understand stationarity. (Weak) Stationarity is defined as having constant expected values and variance and autocovariances that do not ...
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### How to get sample size estimation for two ordinal variables analysed with a linear-by-linear association test?

We would like to confirm a previous result by establishing a new cohort of patients. I compared the distribution of patients among 2 ordinal variables (figure below). One is a biomarker in 3 ...
16 views

### How to do negative binomial regression with the rms package in R? [closed]

How can I use the rms package in R to execute a negative binomial regression? With the MASS package, I use the ...
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### Plot two datasets on the same figure [closed]

I have tried to use t-sne library to visualize data. So I did the following to visualize one dataset: ...
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### How to check for correlation between 5 classes (Likert ratings) and continous variable?

Apologies if the question seems basic or technical terms are used incorrectly, but I am not very experienced in statistics. I have collected data concerning different properties of objects, let's say ...
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### How is it that CLT can be used for around 8 light bulbs?

I have been given the following problem. The light bulbs available have an average lifetime of 1000 hours with a standard deviation of 50 hours. How many light bulbs should we stock so that we can be ...
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### Estimated marginal means with emmeans

I have a mixed linear model, for example, Model <- Values ~ A + B + C + (1 | id) + A:B + A:C + B:C I wanted to do analysis with "emmeans" a.k.a estimated marginal means, so I used these ...
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### How to merge coefficients from Lasso Logit and Logit with different “structure” into one table or data.frame

first off, I am sorry if there was some previous question thats strongly related to this one and likely includes an answer, but the terms I used to look for it did not help. I have conducted an OLS ...
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### interview question: ridge regression the out-of-sample performance never change when tune the hyperparameter?

I happened to an interview question: In Ridge regression, what does it imply if the out-of-sample performance never change however we tune the hyperparameter (the coefficient of L2 regularization)? ...
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### Can Z values be thought of as the number of standard deviations?

I read about the 68-95-99.7 rule that shows I also read that a Z value of 1.96 gives a confidence level of 95% Is it correct to think of Z as the "number of standard deviations" ? Only I ...
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### Analytical Leave-one-out prediction variance for Kriging

I make extensive use of Kriging (Gaussian Process regression) methods in my work especially using the leave-one-out error calculation that you can get from the Gram matrix. Background: To compute the ...
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### Augmetation techniques for satellite image time series

I am considered to apply some augmentation for a set of multivariate data (satellite image time series data) in aim to perform a LULC classification task. However I have some issues and imagination of ...
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### How much precission is required for custom p.d.f. to integrate to one in Stan?

I am in the process of writing a fairly complicated custom probability density function in Stan. The function is composed piece-wise like a spline, and it is impossible to get an integral of it with ...
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### Recreating research paper with HMM and K-S test

I am trying to recreate this research: https://www.mdpi.com/1911-8074/13/12/311/htm My first question is when they present the regime breakdown: ...
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### Demand forecasting task without demand column

I apologize for the naive question in advance, I'm completely new to forecasting. I have a Machine Learning demand forecasting task for a healthcare service. I have some columns such as date, ...
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### When are diagnostics not required for logistic regression?

Logistic regression models (generalised linear models with a binary response) are odd things. I am in the habitat of using randomised quantile residuals (R package statmod) for GLM diagnostics. I have ...
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### Difference in slope in longitudinal study

I have a longitudinal study where subjects are measured at given time points and a response is recorded. Each subject belongs to one of three groups (A, B, C) and I'm interested in whether the slope ...
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### A follow-up to 'The meaning of an analyt. result concerning the… mean of the square of a reciprocal of a norm. distrib. rand. variable'

This question concerns the same subject matter as this previous question of mine. However, a moderator felt that the questions I posed there are significantly different from the question I am about ...
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### What is the advantage of Uplift modeling over the multiple comparison using experimental data?

The ultimate goal of the both methods should be getting the true treatment effect based on different treated groups(i.e.The interaction effect). However, what is the difference between comparing the ...
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### PROBABILITY OF SURVIVAL [closed]

Owing to a medical condition, a man aged 60 is subject to the force of mortality 𝜇𝑥 𝜇60+𝑡 And 𝜇60+𝑡 ′=𝜇60+𝑡+0.05, 𝑓𝑜𝑟𝑎𝑙𝑙𝑡≥0 where, follows the AM196770 Ultimate table. Calculate the ...