Large value of exp (B) in binary logistic regression SPSS what is wrong? [duplicate]

I had a very large value for Exp(B) in SPSS binary logistic regression. What is wrong and what should I do?

• Which value of $B$ is "very large"? The largest one I can see is $0.703$ for "D2(1)", because it is more than twice its standard error, but there is nothing unusual or alarming about that. – whuber Apr 22 '15 at 16:29
• Try search for "complete separation." It seems some of the predictors appear to be a constant or some zero cells were created. – Penguin_Knight Apr 22 '15 at 16:33
• @Penguin_Knight I've created the hauck-donner-effect tag for this express purpose! – Sycorax Apr 22 '15 at 17:10

1 Answer

This usually indicates a problem with Quasi-Complete (categorical variables) or Complete Separation (continuous variables).

Quasi-complete: Where you have one category of a class variable x that has only one type of outcome (y=0 or y=11)

Complete Separation: some breaking point in a continuous variable where target has only one type of outcome on either side. For example, if $x>5$ then y=1 in all cases and if $x\leq 5$ then y=0 in all cases.

• Complete separation is only when you have y=0 for x<c and y=1 for x>=c for some value of c (and 0 and 1 might be flipped) but just having a point where either above or below you only see a single type of response doesn't result in complete separation. – Dason Oct 3 '16 at 17:22
• Right. I guess my answer was not exactly clear on that. updated. – ShainaR Oct 5 '16 at 17:46