I'd like to make a scatterplot with my dependent variable (scores on test A) on the y-axis, age (continuous) on the x-as and group (autism vs. control) as grouping variable, but also subgroup (people above 65 years vs. people younger than 65 years) as grouping variable.
This doesn't seem possible.
The reason I think I need two grouping variables is as follows: with only 'group' as grouping variable, my scatter graph illustrates an interaction effect between age and group. This isn't that weird, because when I run a regression with age, group and agexgroup as predictors, I indeed get the significant interaction effect.
But: this is not what I did in my analysis. I compared models, namely a simple model (3 main effects, 1 interaction effect) and a complex model (same variables as the simple model but with 3 extra interaction effects). I did this in SPSS lineair regression by using 'blocks'. So block 1 was my simple model, block 2 my complex model.
Both of my models doesnt give me any significant interaction effects, not for agexgroup, not for agexsubgroup and not for groupxsubgroup, or agexgroupxsubgroup.
I want to make a scatterplot which is representative for my data outcomes. The scatterplot with the simple agexgroup interaction is not.
Can anyone please help me?