# Questions tagged [separation]

Separation occurs when some classes of a categorical outcome can be perfectly distinguished by a linear combination of other variables.

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### What is the difference between using logistf and brglm2 when dealing with complete separation in a logistic regression?

I am trying to looking at how the three factors A (5 levels, a-e), B (2 levels, a and b) and C (2 levels, a and b) affect the likelihood of event Y (1 = occured, 0 = did not occur). I initially ran a ...
1 vote
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### Analysis of Danish mask study data by Nassim Nicholas Taleb (binomial GLM with complete separation)

Recently, Nassim Nicholas Taleb made this post about the recent Danish mask study, a randomized controlled trial which concluded that the proportions of newly diagnosed coronavirus infections was not ...
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### Are these two 2D datasets the same and can they be separated with the XOR NN?

I'm a very beginner in the neural network topic. So I ran into a problem. I see on the online lectures: Famous example of a simple non-linearly separable data set, the XOR problem (Minsky 1969) in the ...
417 views

### Is this logistf approach the right way to deal with complete separation in my logistic regression?

I am performing lots of association tests between genotypes and binary diseases. The genotypes can be very rare, and my tests often have extreme case control imbalance (e.g. 500 controls for every ...
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### Using Chi-squared test when perfect separation in logistic model?

My dataset is similar to this; it describes the presence/absence of a parasite in six species of animal from two locations. Each row in the dataset represents a different individual animal. I would ...
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1 vote
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### penalised logistic regression with brglm - warnings

I've built a logistic model to predict a binary response. I've got four categorical predictors. One of them (posicion) has 6 levels, 3 of which occur not too frequently and are ALWAYS (by definition) ...
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### Unexpected behaviour of logit regression with glm in R

I recently was puzzled by the behaviour of R's glm when trying to compute a logistic regression ...
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1 vote
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### Separation and Correlation

In a logistic regression setting, can there be a relation between the fact that covariates are highly correlated and the problem of perfect(quasi-perfect) separation?
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### What is the cause of this very high standard error in my logistic regression model?

I am running a logistic regression model where the outcome variable is Neurologic Complications, and there are various factors who's impact I am examining. One of the factors (HTN_new1), a categorical ...
205 views

### Probability of linear separation in a dataset with categorical response

I am simulating datasets to which I fit polytomous logistic regression models. The maximum likelihood estimator of this model is undefined when all categories are linearly separated (and it is quite ...
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### What does it means getting p-values equal to 1 and complete separation in logistic regression? [duplicate]

I was really confused if I should ask this here or in Stackoverflow, but I'll give a shot here. I ran a logistic regression using statsmodels library in Python. However, two things went wrong here (...
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### Separating hardly distinguishable classes for easier classification

I apologize for this seemingly basic question, but I was just thrust into this data science role and would like to get some advice from some experts. I have a dataset with a small number of features ...
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### Logistic Regression assumption

In Logistic Regression, the assumption is that the data must be linearly separable, but if the data is not linearly separable then we can't apply Logistic Regression?
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### Fourier analysis to retrieve components of individual spectra

I have a basic, simple question, I am a physics student, and searching internet gives me a lot of signal processing theory but couldn't find this basic answer, which I plan to implement in my speech ...
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### Cumulative explained variance between scaled and unscaled data

I was writing a small piece of code to portray the difference between scaled and unscaled data when doing PCA and (as expected) I found that the separability of classes was better by doing the ...
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### instability of logistic regression

I am reading Introduction to Statistical Learning and it is said (as in other websites) that Logistic Regression is unstable compared to Linear Discriminant Analysis in well separated cases. ...
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1 vote