[R] Bias in sample - Logistic Regression

Maithili Shiva maithili_shiva at yahoo.com
Wed Oct 1 07:27:36 CEST 2008

Hi. This is my first mail. I am new to R and also to the company where I am employed now. I have Statistics background (i.e. Master of Science). 

However, it is only now I understand what I learned in text is simply a bookish knowledge and when it comes to actually applying statistics in real life, things are not simple. But I am sure I will accordingly upgrade myself.

In my new company, I had been assigned a task of developing credit scoring model. Using logistic regression and using R Language, I have estimated the regression coefficients etc and arrived at the probability of default using the significant variables (or attributes).

However, as a part of validating the model, I have been asked to find out if there is any bias in the sample data (I have used for logistic regression) and to use REJECT INFERENCE.

For me this is really new and I am really helpless at this moment as also my confirmation will take place based on this model developed. I sincerely appreciate if someone guide me as to how do I proceed and use this concept of "Reject inference". I did surf the net, but whatever information I could gather, was not sufficient. Also please suggest if there is any other measure in R, I can use to find out if my sample is bias free. 

I wish to bring to your kind notice that, I had constructed the sample (for customer data) using the various variables like Sex, Gross Income, no of dependents etc. and while construding this data, I had used the random numbers.

I thank you in advance and sincerely apologise for this long mail. Please someone help me out.


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