Equation for differences between suppliers

[SylvainVrolijk]

Hello,

I have a dataset with data from three different suppliers. I want to see if there are differences with the suppliers as the independant variables.
I tried giving them dummy variables in excel (1 and 0) but it gives me a near perfect collinearity error.

Does anyone know how I can bypass this?

Thanks in advance

[startz]

Take out the constant term.

[SylvainVrolijk]

Thank you