when to use a log log regression model?

the book says whenever the dependent variable bears a contstant propotional relationship with independent variable

can some1 explain it more clearly?

when to use a log log regression model?

the book says whenever the dependent variable bears a contstant propotional relationship with independent variable

can some1 explain it more clearly?

If

*y* = *c*(*x*^*m*)

then

log(*y*) = log[*c*(*x*^*m*)] = log(*c*) + *m* log(*x*)

If we let *Y* = log(*y*), *b* = log(*c*), and *X* = log(*x*), then we have:

*Y* = *mX* + *b*

which is a straight line.

ok so if the relationship is something which is explained by raising the dependent variable to a power than we use log log reg. model?

Yup.