  We study a 24\,$\mu$m selected sample of 330 galaxies observed with the
Infrared Spectrograph for the 5\,mJy Unbiased Spitzer Extragalactic Survey. We
estimate accurate total infrared luminosities by combining mid-IR spectroscopy
and mid-to-far infrared photometry, and by utilizing new empirical spectral
templates from {\em Spitzer} data. The infrared luminosities of this sample
range mostly from 10$^9$L$_\odot$ to $10^{13.5}$L$_\odot$, with 83% in the
range 10$^{10}$L$_\odot$$<$L$_{\rm IR}$$<10^{12}$L$_\odot$. The redshifts range
from 0.008 to 4.27, with a median of 0.144. The equivalent widths of the
6.2\,$\mu$m aromatic feature have a bimodal distribution. We use the
6.2\,$\mu$m PAH EW to classify our objects as SB-dominated (44%), SB-AGN
composite (22%), and AGN-dominated (34%). The high EW objects (SB-dominated)
tend to have steeper mid-IR to far-IR spectral slopes and lower L$_{\rm IR}$
and redshifts. The low EW objects (AGN-dominated) tend to have less steep
spectral slopes and higher L$_{\rm IR}$ and redshifts. This dichotomy leads to
a gross correlation between EW and slope, which does not hold within either
group. AGN dominated sources tend to have lower log(L$_{\rm PAH 7.7\mu
m}$/L$_{\rm PAH 11.3\mu m}$) ratios than star-forming galaxies, possibly due to
preferential destruction of the smaller aromatics by the AGN. The log(L$_{\rm
PAH 7.7\mu m}$/L$_{\rm PAH 11.3\mu m}$) ratios for star-forming galaxies are
lower in our sample than the ratios measured from the nuclear spectra of nearby
normal galaxies, most probably indicating a difference in the ionization state
or grain size distribution between the nuclear regions and the entire galaxy.
Finally, we provide a calibration relating the monochromatic 5.8, 8, 14 and
24um continuum or Aromatic Feature luminosity to L$_{\rm IR}$ for different
types of objects.

Cosmology and Nongalactic Astrophysics