# problems in doing logistic regression with unbalanced sample, give me some references [duplicate]

I have a dataset with lots Y=0 and few Y=1. I have to run logistic regression, so I'm using a retrospective sample in order to get a more balanced sample. Could someone give me some references that explain which are the problems arising when I use logistic regression in an unbalanced sample? I kwow that the main problems are instability of estimated coefficients and poor predictive power of the model, but I need some references.

## marked as duplicate by kjetil b halvorsen, Peter Flom♦Nov 3 '16 at 12:08

• The problem is the few $Y=1$ rather than the many $Y=0$. See here. If you already have the data, there's no benefit to throwing some of it away. – Scortchi Mar 28 '15 at 11:27