Tagged Questions

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error in logistic regression

I am new to this forum and beginner in Matlab implementation. Kindly, if some one can help me out why my accuracy isn't increasing in training. My problem is as follow: Implement an optical character ...
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Poisson or binomial regression?

I have a binary response variable (it is a presence/absence variable) and a ordinal discrete predictor: ...
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Ordinal regression models vs. nominal regression models

Suppose we are trying to decide whether to use an ordinal regression model or a nominal regression model. If we know that the outcome variable is ordered should we still use a nominal regression model ...
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Steps followed when Binary logistic regression when both dependent and independent variables are binary

I had set of binary variables. To apply logistic regression, I have checked association between dependent and independent variables and considered only those independent variables in the model which ...
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Methods / approach to improve the predictive accuracy of a logistic regression model

The situation: I have a logistic model that should predict a defect (1=defect, 0=no defect). My model uses 4 out of 14 parameters, which are significant for my ...
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Statistical tools to be used for small data sets

I am a newbie to statistics. I am trying to model admission criteria for B-School based on one past years data. It has roughly 370 samples. I am trying to set admission criteria taking their ...
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How to solve this binomial regression problem

Suppose you have a set of observations that are assumed to be binomial distributed, according to the following rule: $$t_i = \text{Binomial}(n_i,k_i,\phi) \text{ } \forall i \in (1,...,N)$$ $\phi$ ...
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conditional logistic regression to analyze a case-control study

I am analyzing a case-control study on patient given dose effect to outcome (recovery or not). The control patients were matched according to age (5-year per category) and performance status (PS). As ...
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Which one to use Splines / Interaction or both?

I am modeling a binary event of whether a sale will happen or not for an online retailer. I have millions of clicks to refer to. Needless to say the rate of sales happening is very very low (<1%). ...
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Logistic Regression and Inflection Point

We have data with a binary outcome and some covariates. I used logistic regression to model the data. Just a simple analysis, nothing extraordinary. The final output is supposed to be a dose-response ...
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Logistic regression prediction validation

I am try to evaluate a logistic regression with new data using R. I have created the logistic regression using the old data and evaluated that using chi^2 etc. i.e. ...
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Multinomial logistic regression for big data

How do I go about doing a multinomial logistic regression when I have 70 million observations? Is it feasible? It seems that R is out of the question due to memory constraints?
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Logistic regression and maximum entropy

I have read (e.g. here) that a (multinomial) logistic regressor corresponds to a maximum entropy classifier. My question is, how does one end up with the formula for logistic regression starting with ...
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Does undersampling help to build a better model?

To reduce the load on the machine I want to take the benefit of the undersampling approach. Here are a few facts about my data: My data is of the order of 20 millions or even more. The event rate ...
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Use of linear regression or logistic regression when testing conditioned group differences

Background I have a colleague interested in a particular disease and specifically if the continuous variable $X$ is different between controls and patients. Preliminary results suggest that patients ...
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How to treat a time rank in logistic regression?

For an analysis of user attrition I want to perform a logistic regression, using task difficulty and point in time (100 trials) for a math task. My guess is that high difficulty at a late point in ...
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“Bayesglm”, p-values and degrees of freedom?

I am trying to perform some logistic regressions (and I am a neophyte user of R). Initially I used "glm" to compute coefficients, AIC and p-values; this worked great until I ran across a data set ...
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Inverted SPSS results: Logistic regression command vs. Genlin?

I want to do a logistic regression in SPSS. However, since I analyse unemployment spells the subjects are sometimes repeated (violating the independence assumption of the regression). One way of ...
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How high must logistic covariates' predictive accuracy be for a reversal effect to show up?

I am modeling an outcome for hospital patients, 'RA' (whether readmitted; 0=No, 1=Yes). My predictor of interest is 'HHS' (whether referred to Home Health Services such as from a visiting nurse; ...
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Concordance and Discordance role in modelling

I am new to statistics and was asked to develop a statistical model, which I had started, they ask me to carry out concordance and discordance now, however I don't know anything about these terms ...
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Geometric Interpretation of Softmax Regression

I'm writing a series of blog posts on the basics of machine learning, just for fun, mostly to validate my understanding of Andrew Ng's class. As I'm currently studying generalized linear models ...
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Logistic regression with partially observed variables

Let's say I have a binary variable to explain using "some" logistic regression approach. The set of variables I have at disposal are exhaustive for a given period of time and for a longer period a ...
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Concerns about the size of odds-ratio estimates in binary logistic regression model

I am creating some binary regressions and am wondering if I should be surprised by the size of the odds ratios. In this particular example, the dependent variable indicates whether a student can ...