Short version:
Does including a categorical nominal-level independent variable WITHOUT dummies still work as a simple control for other independent variables?
e.g. for P = b0 + b1*Grades + b2*WordCount + b3*Sex + b4*Major
With 6 possible categories for Major, I know b4 is meaningless since Major is categorical. But do the coefficients for b1, b2, b3 still remain meaningful? i.e. b1 is the change in P for each unit change in Grades, holding all else constant, controlling for WordCount, Sex, and Major; etc.?
Longer version:
I am running a multiple linear regression on plagiarism (as a percentage P) as dependent variable, and independent variables Grades, WordCount, Sex, Major:
P = b0 + b1*Grades + b2*WordCount + b3*Sex + b4*Major
As such, Sex is a simple 0/1 dummy variable.
My issue is with Major, which is a categorical nominal-level variable, currently labeled 1 through 6.
Alas with my messy data, going the dummy variable route (5 0/1 dummy variables for 5 majors with an excluded baseline major, i.e. equivalent to reg P Grades WordCount Sex i.Major in Stata) makes the WordCount coefficient statistically insignificant. For some reason, just including the Major variable as-is (i.e. reg P Grades WordCount Sex i.Major in Stata) makes the WordCount coefficient statistically significant. Is this significant coefficient meaningful?
Thanks in advance!
Does including a categorical nominal-level independent variable WITHOUT dummies still work as a simple control for other independent variables?
e.g. for P = b0 + b1*Grades + b2*WordCount + b3*Sex + b4*Major
With 6 possible categories for Major, I know b4 is meaningless since Major is categorical. But do the coefficients for b1, b2, b3 still remain meaningful? i.e. b1 is the change in P for each unit change in Grades, holding all else constant, controlling for WordCount, Sex, and Major; etc.?
Longer version:
I am running a multiple linear regression on plagiarism (as a percentage P) as dependent variable, and independent variables Grades, WordCount, Sex, Major:
P = b0 + b1*Grades + b2*WordCount + b3*Sex + b4*Major
As such, Sex is a simple 0/1 dummy variable.
My issue is with Major, which is a categorical nominal-level variable, currently labeled 1 through 6.
Alas with my messy data, going the dummy variable route (5 0/1 dummy variables for 5 majors with an excluded baseline major, i.e. equivalent to reg P Grades WordCount Sex i.Major in Stata) makes the WordCount coefficient statistically insignificant. For some reason, just including the Major variable as-is (i.e. reg P Grades WordCount Sex i.Major in Stata) makes the WordCount coefficient statistically significant. Is this significant coefficient meaningful?
Thanks in advance!