Linked Questions

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1answer
783 views

perfect separation logistic regression [duplicate]

in continuity to the post stepwise logistic regression non significative variables(high p-values) and as demanded by matthew this is a post explaining the data i have and the problem in fact i have a ...
1
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0answers
289 views

How to detect perfect separation of logistic regression? [duplicate]

I have same error message as in this post. However all my coefficients look normal with no inflated value or standard errors. My question is how can I make sure the error message is a sign of perfect ...
46
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2answers
116k views

Logistic regression model does not converge

I've got some data about airline flights (in a data frame called flights) and I would like to see if the flight time has any effect on the probability of a ...
22
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1answer
5k views

Is there any intuitive explanation of why logistic regression will not work for perfect separation case? And why adding regularization will fix it?

We have many good discussions about perfect separation in logistic regression. Such as, Logistic regression in R resulted in perfect separation (Hauck-Donner phenomenon). Now what? and Logistic ...
20
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1answer
13k views

Understanding complete separation for logistic regression [duplicate]

Why does logistic regression not converge for a linearly separable data set? For linear separable data sets the model parameters go to infinity when mimizing the error function (according to ...
4
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3answers
1k views

Unstable logistic regression when data not well separated

There are some good answers discussing convergence issues of logistic regression when the data are well separated here and here. I am wondering what can cause convergence issues when the data are not ...
8
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1answer
3k views

How to describe and present the issue of perfect separation?

Folks who work with logistic regression are familiar with the issue of perfect separation: if you have a variable specific values of which are associated with only one of the two outcomes (say a ...
4
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1answer
396 views

Why one result is so wide in this logistic multiple regession

I am doing multiple logistic regression with data with 24 predictor variables and 193 rows. All predictor variables have values of 0 or 1 and outcome variables (OUTVAR) also has only 2 possibilities. ...
6
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1answer
1k views

Perfect separation error message for glm with binomial but not with quasibinomial family

I am attempting to create a model which looks at the effect that age, supplementary food use, and nest initiation date (converted to Julian days) is having on female reproductive success (success =1 ...
3
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1answer
1k views

Iteratively Reweighted Least squares for logistic regression when features are dependent?

I was solving logistic regression using IRLS (wiki) described in the wiki link. Now I have a doubt, if $X$ has dependent features then $X^TS_kX$ will not have full rank and thus will not be invertible ...
3
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1answer
613 views

Connections between Logistic Regression and Linear Programming

This post Testing for Linear Separability with Linear Programming in R, discusses using linear programming to test if data is linear separable. What's the connection (if there are any) between LP ...
1
vote
1answer
449 views

If logistic regression is a linear classifier why does it fail on linearly separable data?

Logistic regression is a linear model, decision boundary generated is linear. If the data points are linearly separable, then why does Logistic regression fail? Shouldn't it perform better on data ...
3
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2answers
185 views

Binomial GLM - non-significant difference between 100% opposite groups of observations

What follows is a basic question concerning Binomial GLM's. Suppose we have a set of observations where a binary response was measured in three different treatments, A, C and D - ...
3
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1answer
50 views

Ordinal Logistic Regression: is it normal to find very high coefficients?

I am running an ordinal logistic regression in R to assess the effect of 3 IVs (GDP, n. of bilateral agreements, HDI - all in log) on the diplomatic ranking (DV) ascribed to different countries (...
1
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1answer
54 views

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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