I was going through a tutorial here and it has the below info
"Controlling for a variable” means modelling control variable data along with independent and dependent variable data in regression analyses and ANCOVAs. That way, you can isolate the control variable’s effects from the relationship between the variables of interest.
Example: Statistical control. you collect data on your main variables of interest, income and happiness, and on your control variables of age, marital status, and health. In a multiple linear regression analysis, you add all control variables along with the independent variable as predictors. The results tell you how much happiness can be predicted by income, while holding age, marital status, and health fixed."
What I didn't understand is how do they say that
marital status and
health are fixed?
In my dataset, I have information for subjects' income, happiness, age, marital_status and health.
While I understand we are trying to study the association of
happiness, may I know how can
health be constant?
All my subjects have varying values for
How come collecting data about
control variables and putting them in regression equation makes them
can help me with an example pleasE?>