# Tagged Questions

Refers generally to statistical procedures that utilize the logistic function, most commonly various forms of logistic regression

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### Luce choice axiom, question about conditional probability

I'm reading Luce (1959). Then I found this statement: When a person chooses among alternatives, very often their responses appear to be governed by probabilities that are conditioned on the ...
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### How to test for mediation when working with binary data?

I want to assess if a single variable is mediating the effects of a set of IVs on a single DV. All variables in the model (IV, DV and the mediator variable) are dichotomous (0, 1) and observed. What ...
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### How can I assess GEE/logistic model fit when covariates have some missing data?

I have fit two generalized estimating equation (GEE) models to my data: 1) Model 1: Outcome is longitudinal Yes/No variable (A) (year 1,2,3,4,5) with longitudinal continuous predictor (B) for years ...
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### Inference on fixed effects in a mixed effects model

I have correlated data and am using a logistic regression mixed effects model to estimate the individual level (conditional) effect for a predictor of interest. I know that for standard marginal ...
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### Maximum entropy classifier and sentiment analysis

I am doing a project work in sentiment analysis (on Twitter data) using machine learning approach. In order to find the 'best' way to this I have experimented with naive Bayesian and maximum entropy ...
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### Updating classification probability in logistic regression through time

I am building a predictive model that forecasts a student's probability of success at the end of a term. I’m specifically interested in whether the student succeeds or fails, where success is usually ...
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### Using a set of binary logistic regressions with multiple choice categorical response variable

I have categorical survey data on people's attitudes towards a certain policy area from 13 countries. The response variable is categorical, and includes 4 distinct answers that cannot be ordered. I ...
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### Assumptions of generalized linear models

On page 232 of "An R companion to applied regression" Fox and Weisberg note Only the Gaussian family has constant variance, and in all other GLMs the conditional variance of y at $\bf{x}$ ...
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### Probabilities from Logistic Regression

I have built a logistic regression model in R and though the result appears to be satisfactory to some degree, there is one question I have not be able to address. I am not sure if my approach is at ...
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### Numerical properties of the logistic growth model for non-linear regression

I am using the nls procedure in R to fit a logistic growth model. In their SSlogis function, José Pinheiro and Douglas Bates chose the formulation ...
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### Normalize binary features for logistic regression

I am applying logistic regression and I am using a mixture of continuous and binary features. My question would be how do you go about binary features when trying to normalize. I would very much ...
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### (Why) should bootstrap sampling distribution for logistic regression slope be conditional on $S=\sum Y_j$?

I am working my way through Chapter 4 (Tests) in Davison & Hinkley's (D&H's) book "Bootstrap Methods and their Applications", and have a question about one of their examples. Davison & ...
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### Is standardization needed before fitting logistic regression?

My question is do we need to standardize the data set to make sure all variables have the same scale, between [0,1], before fitting logistic regression. The formula is ...
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### Logistic regression model for analysis of many IVs with a relatively small sample size

I'm trying to determine the influence (direction and relative strength) of certain attributes of incoming students to an academic program on their successful completion of the program. My sample size ...
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### Making new variable instead of correcting for temporal autocorrelation in a GLMM. Is it a valid alternative?

I am doing some forest disturbance research, in which the aim is to predict the probabilities of wind damage occurrence in forest stands of different site (altitude, slope steepness) and stand ...
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### Crossed random effects and unbalanced data

I am modeling some data where I think I have two crossed random effects. But the data set is not balanced, and I'm not sure what needs to be done to account for it. My data is a set of events. An ...
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### How to assess mediation effect in multinomial logistic regression?

I wonder if it possible to include a mediation effect in multinomial logistic regression. I have a categorical (3 categories) outcome variable and four predictors (all continuous). I expect one of the ...
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### 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 ...
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### Proper Sampling - can I collect a two-group sample this way without issues?

I need to collect a two group sample for a comparison analysis (perhaps using logistic regression). The population that I need to extract a sample from is all firms from country A with activities in ...
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### Cross validation for lasso logistic regression

I am writing a routine for logistic regression with lasso in matlab. So the problem is to minimize the negative log-likelihood function with the penalty term ...
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### What does a huge gap between P values of the same predictor computed in bootstrapped and non-bootstrapped versions of the same regression mean?

My binary logistic regression gives P values significant at 0.05 level for some of the modeled independent variables. However, bootstrapping the same regression model gives P values significant at ...
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### Fractional Polynomial interpreting interaction terms

Background: I have developed a logistic regression model where I am trying to analyze the effect of socio-economic data of a family on their probability of receiving a home loan. I have used ...
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### Separation in logistic regression in a complex survey?

Firth's penalized maximum likelihood estimates, exact logistic regression and Bayesian logistic regression (e.g. bayesglm) can account for separation in logistic regression. But how to account for ...
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### Variable selection / Dataset reduction for large datasets (in R)

I'm working on a behavoural scorecard modelling exercise, and many of the decisions taken to date have been based on the experience of a consulting credit analyst (whose experience software-wise is ...
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### Generalization of cumulative probability models for ordinal Y

There are many models in existence for ordinal $Y$, for example the proportional odds ordinal logistic model, the continuation ratio model, and the cumulative probit model. The first and third of ...
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### Analysis of randomized experiments

I have data from an experiment in which participants were randomly assigned to one of two groups and asked a series of opinion questions. One group, the control, was not presented with any additional ...
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### Modeling pass rates for departments and courses within a school

Suppose I have a regression model, for example a logistic regression model, which provides a score between 0 and 1 reflecting whether or not that a student will pass a course given certain variables: ...
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### Using priors to detect an effect? logistic Bayesian regression

I have designed an idea and am looking for similar approaches in other literature/areas or if I have applied the Bayesian concepts wrongly. Here is a statement of my problem: I am modeling the ...
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### How to test proportions of a Categorical response variable for a Repeated measures design with Unequal Sample Size?

I have a question about the analysis of a unequal sample size repeated measures data with categorical response variable. This experiment looks at 5 young and aged persons and for each of the ...
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### Logistic Regression Cost Function issue in Matlab

I'm trying to implement a logistic regression function in matlab. I calculated the theta values, linear regression cost function is converging and then I use those parameters in logistic regression ...
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### Sensible to include ratio as a variable in logistic regression?

I'm creating a generalised linear regression using a binomial link function for two variables A and B. From looking at the data it appears that A/B may have discriminatory effect. Is it sensible to ...
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### Shifted intercepts in logistic regression

I have a question about the effects of shifting the intercept in a logistic fit on the mean of a particular transformation of the scores. Here is the notation I will be using for the question. The ...
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### Validating a logistic regression for a specific $x$

I have a logistic regression model for 0/1 binary response data that is built from samples $(x_1,Y_1),\ldots,(x_m,Y_m)$, where $x_1,\ldots,x_m$ are, fixed, nonrandom, real values and $Y_1,\ldots,Y_m$ ...
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### Bayesian model averaging in R

I have a logistic model that I've built with the nls function in R. I want to use Bayesian model averaging for variable selection, but I can't find a package for ...
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### Dependent variable maximum value contingent on independent variable

I am trying to create a model for debt collections. In the past I have used logistic regression to predict pay/no-pay. This has worked well but has a few unfortunate consequences. People are more ...
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### What is the effect of merging categories on logistic regression estimates?

I have a logistic regression with a number of predictors variables including a factor with, say, 5 categories. The estimates for that factor compare categories 2-5 in turn to the reference category ...
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### What diagnostics for random effects logistic regression?

I'm wondering what checks/diagnostics you usually calculate and report if you do a random effects logistic regression. C-statistic/ROC curve Check multicollinearity? Check heteroscedasticity? ...
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### May I validate a model after shrinkage?

I am doing a logistic regression using Frank Harrell's rms package. I went through the steps shown in his book and the rms ...