  The Z line shape is measured at LEP with an accuracy at the per mille level.
Usually it is described in the Standard Model of electroweak interactions with
account of quantum corrections. Alternatively, one may attempt different
model-independent approaches in order to extract quantities like mass and width
of the Z boson. If a fit deviates from that in the standard approach, this may
give hints for New Physics contributions. I describe two model-independent
approaches and compare their applications to LEP data with the Standard Model
approach.
