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!
note: also under discussion in "Talk Stats Forum"