We examine the fermion asymmetry measurements at LEP and SLC leading to effective weak mixing angle, sin 2θ eff . We notice very interesting regularity in these measurements. All asymmetry measurements fall into two classes. Class A measurements where hadronisation effects are not relevant for the final result and class B measurements where hadronisation effects cannot be avoided and can only be corrected with whatever understanding of these phenomena we have. In each of these classes there is excellent agreement between LEP and SLC results. However the two classes are distinctly apart by more than 3σ. We suggest that for precision test of the Standard Model the class A measurements should be preferred.
Precision test of the standard model on the toponium resonance
