I am a very beginner of statistic. Recently a project require me to analyse data using logistic regression & SPSS within a specific time frame. Although I have read few books, but still very blur on how to start off. Can someone guide me through? What is the 1st ste and what next?
Anyway, I have started some. Once entered the data into SPSS, I have done crosstab (categorical IV), descriptive (continuous IV) and spearman correlation.
Then, I proceed to test for nonlinearity by transforming into Ln which give me some problems. I have re-coded all zero cells to a small value (0.0001) to enable the Ln transformation. Then, I re-test the nonlinearity.
Question:
1) The only solution for violation is to transform the variable from continuous to categorical? I got one violation.
2) One Exp(B) is extremely large (15203.835). What does this means? Why?
3) There is one interaction has Exp(B) = 0.00. Why?
Many thanks.
Best Answer
Generally large beta coefficients signal multi-collinearity. You should look for marginals that are zero in your cross-tabulations. You should also pay attention to mpiktas's comment. Testing for linearity (and transforming to categorical) is not generally needed if you have been setting up your data correctly.