  In this paper we compare two regression curves by measuring their difference
by the area between the two curves, represented by their $L^1$-distance. We
develop asymptotic confidence intervals for this measure and statistical tests
to investigate the similarity/equivalence of the two curves. Bootstrap
methodology specifically designed for equivalence testing is developed to
obtain procedures with good finite sample properties and its consistency is
rigorously proved. The finite sample properties are investigated by means of a
small simulation study.
