  We analyze the corrections to the precision EW observables in minimal
composite Higgs models by using a general effective parametrization which also
includes the lightest fermionic resonances. A new, possibly large,
logarithmically divergent contribution to S is identified, which comes purely
from the strong dynamics. It can be interpreted as a running of S induced by
the non-renormalizable Higgs interactions due to the non-linear sigma-model
structure. As expected, the corrections to the T parameter coming from fermion
loops are finite and dominated by the contributions of the lightest composite
states. The fit of the oblique parameters suggests a rather stringent lower
bound on the sigma-model scale f > 750GeV. The corrections to the Z bL bL
vertex coming from the lowest-order operators in the effective Lagrangian are
finite and somewhat correlated to the corrections to T. Large additional
contributions are generated by contact interactions with 4 composite fermions.
In this case a logarithmic divergence can be generated and the correlation with
T is removed. We also analyze the tree-level corrections to the top couplings,
which are expected to be large due to the sizable degree of compositeness of
the third generation quarks. We find that for a moderate amount of tuning the
deviation in Vtb can be of order 5% while the distortion of the Z tL tL vertex
can be 10%.
