as SDSS/SEGUE spectra (stars) throughout this paper.

Since this stellar database includes stars in many evolutionary stages and spans a wide range of metallicity ($-4.0 <$ \[Fe/H\] $< +0.5$), measurement of the carbon-to-iron ratios enables the determination of the frequency of the CEMP phenomenon for stars of various spectral types, luminosity classes, and metallicities. This should, in turn, provide valuable constraints on Galactic chemical evolution models, numerical simulations of Galaxy formation, the nature of the IMF at early times, and the various proposed carbon-production mechanisms.

In this paper, we present new techniques for the measurement of [\[C/Fe\]]{}, and derive the frequency of CEMP stars from the large sample of SDSS/SEGUE spectra. Section 2 describes our methodology for estimation of [\[C/Fe\]]{}. A validation of this method, based on a star-by-star comparison with high-resolution spectroscopy of SDSS/SEGUE stars in the literature, is provided in Section 3. The impact of signal-to-noise ratios (S/Ns) on the measured [\[C/Fe\]]{} is also examined in Section 3. Section 4 derives the frequency of the CEMP stars, as a function of [\[Fe/H\]]{}, for the full sample, as well as for stars in various luminosity classes. A summary of our results and our conclusions are provided in Section 5.

