I'm doing a study where I need to research if X1/X2 has an increasing influence on Y when the educational level rises. Next to this I'm also interested which X has the greater influence on Y.

My current model is the following:

Y = constant + β1X1 + β2X2 + β3X3 + β4X4 +β5X5 + β6X1X3 + β7X1X4 +β8X2X5 +β9X2X3 + β10X2X4 +β11X2X5

Where X1 and X2 are the independant variables X3, X4 and X5 are the educational levels based on dummy variables, the educational level is categorical. The rest are interactions between the 2 types above.

However when I use this model in SPSS as a linear regression none of my variables or interactions are significant.

My question is how can I solve this and if I need another type of model, how can I check which type fits best? And if I need another type of model, which one do I need to use?

I also have data about sex, age, wages and position which could be introduced into the model as well.

Kind regards