Hello everyone,

I have a logistic regression with an extensive set of control variables. My dependent variable is electoral turnout in an election and one of my indepedent variables is a continious variable for age. In the country of interest, age shows a curvliniear relationship to electoral turnout and therefore, I also want to include age squared. My issue is that when I have the logistic regression without the age squared, the relationship between electoral turnout and age shows a positive and not statistically significant relationship. However, when I include age squared as well, the variable age (not squared) is negative and statistically significant, while age squared shows a positive and statistically significant relationship. Normally, the age variable "should be" positive. Is it "normal" that the original variable shows a negative relationship, while the squared variable shows a positive relationship, or vice versa? Or is this because I've done something wrong? I can't see any problems with the age and aqe squared variable.

The first picture shows with the squared variable excluded and the second picture with the age squared variable included. "ålderkont" is the not squared variable, while "ålderkont2" is the squared variable.
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Thank you very much in advance.

Best regards,
Kajsa