  We show how precision electroweak data, assuming CP conservation and flavor
universality, despite being sensitive to 20 dimension 6 operators, constrain
severely only 9 combinations of them. We define a set of 7 oblique parameters
$\hat S, \hat T, \hat U, V, X,W,Y$ which fully describe corrections to the
leptonic observables. We add two additional parameters $\delta \epsilon_q,
\delta C_q$ to take into account the most precise hadronic observables. Another
parameter $\delta \epsilon_b$ is considered for the bottom quark if flavor
universality is not assumed for the third generation of quarks. We show that
the approximation is extremely satisfactory testing it on a set of random new
physics models and on some famous $Z'$ gauge bosons.
