# Quasi-complete separation

I have a question regarding quasi-complete separated data.

One example of quasi-complete separation is a dataset, where all x < 2 have y=1, all x > 2 have y=0 and some x=2 have y=0 and some x=2 have y=1.

I have a dataset with kind of the following situation: for all x < 2 y=0, for all x > 5 y=1. In the rage x=2 to x=5 y is sometimes zero and sometimes one.

Is this a case of quasi-complete separation as well?

Does is matter for logistic regression if the range of x=2 to x=5, where y varies, is small?

An example how my data look like: ## 1 Answer

Your textual description ("for all x < 2 y=0, for all x > 5 y=1. In the rage x=2 to x=5 y is sometimes zero and sometimes one") does not match your figure. All data displayed in the figure have x<2, and many have y=1. Nonetheless, neither your textual description nor the figure have separation or quasi separation. For both your description and the figure, the data where y=0 and where y=1 overlap. Logistic regression will have no problems with these data.