# Excel and SPSS return opposite coefficients

I am getting familiar with SPSS, specifically the Automatic Linear Modeling functionality. I first ran SPSS, using Best Subset method which gives me the result of "best" variables. Being uncertain, I run again in Excel with the same data. Much to my surprise, the coefficients of one variable are not the same: they are the opposite of each other, having identical attributes. I am ok with the different intercepts but opposite coefficients imply very different stories about the data.

What is the meaning of this? What did I do wrong? What model should be used? Does this mean I have to check again everytime SPSS return a model from best subset functionality?

This is the transformation summary.

Role (Summer_transformed) Predictor

Actions Taken (Summer_transformed) Change measurement level from continuous to ordinal

Role (Month_transformed) Predictor

Actions Taken (CK_transformed) Trim outliers

Actions Taken (Month_transformed) Trim outliers

Role (CK_transformed) Predictor

It seems that SPSS uses summer_transformed=1 as the reference group, while Excel uses summer_transformed=0. You can see that the difference in intercepts is also equal to the difference between these groups, so once you correct the reference, you should get exactly the same results.