  We present criteria to detect the depth of entanglement in macroscopic
ensembles of spin-j particles using the variance and second moments of the
collective spin components. The class of states detected goes beyond
traditional spin-squeezed states by including Dicke states and other
unpolarized states. The criteria derived are easy to evaluate numerically even
for systems of very many particles and outperform past approaches, especially
in practical situations where noise is present. We also derive analytic lower
bounds based on the linearization of our criteria, which make it possible to
define spin-squeezing parameters for Dicke states. In addition, we obtain spin
squeezing parameters also from the condition derived in [A. S. Sorensen and K.
Molmer, Phys. Rev. Lett. 86, 4431 (2001)]. We also extend our results to
systems with fluctuating number of particles.
