Following the advice here regarding statistical significance versus substantive meaning of a model, I did a scatterplot with 'fit line at subgroups'.
My graph clearly shows that there is an interaction between X1 and X2 on Y. However, the F test of the X1*X2 interaction is insignificant. I am using SPSS GLM. X1 is significant but X2 is insignificant and the product term (X1*X2) is insignificant as well.
Question: How do I reconcile these contradictory outcomes? (i.e. see an interaction in the graph but not seeing a significant F test result in GLM)
I understand the importance of substantive meaning. However, sooner or later, someone may ask me why I am graphing the X1 and X2 on Y when the product term is insignificant.
(In the Parameter Estimates table in the SPSS GLM outcome, the t test for each level of X1 with X2 (e.g. maleX1 and femaleX1) is signficant.)
Please see graph below: