3)"A linear regression model is of the form:

Y = β0 + (β1)(X1) + (β2)(X2) + ... + (βk)(Xk) + ε

If there is more than one independent variable, then the model is called a MULTIPLE linear regression model."

This idea doesn't seem too clear to me. Here, what can the Xi's be? What are some specific examples of mutliple linear model? Does a linear model always have to be a straight line or a plane?

Thanks for clearing my doubts!

β

ε

note: also under discussion in "Talk Stats Forum"