Simple Logistic Regression

#1
Hey everyone,

I had a question with respect to SLR.

In Block 0: my classification table predicts 89.3%
In Block 1: my classification table predicts 89.3%

Here's a screen shot of the two: http://s10.postimg.org/ykqsieqt5/block1vsblock2t_1.jpg

I am new to logistic regression so I am having difficulty believing this should be accurate.

Thanks for your input in advance.

Cheers!

P.S. Not sure if I should have posted this in the SPSS forum or not. If it belongs there then feel free to move it obviously
 

hlsmith

Omega Contributor
#2
What is SLR? What are the blocks supposed to represent?

Your model is a little wonky with nobody predicted not to have the outcome?
 

maartenbuis

TS Contributor
#3
I suspect that SLR stands for Simple Logistic Regression. However, I don't know what "simple" is suposed to mean; doest that mean that there is also Difficult Logistic Regression?

Anyhow, your result is pretty common, and it shows how useless classification tables are. If an outcome is rare, as in your case 10.7%, you can correctly predict the outcome for 89.3% by assigning everybody to the "fail" category. This is what both models have done. You would have gotten the same result if you added no variables at all. So using this criterium you could conclude that your two models are as good / as bad as a model with no explanatory variables. It is not so bad, as it is very hard for models to improve on an empty model with this metric. This means that there is something wrong with the metric and not necessarily with your model.