  The analysis of Type Ia supernova data over the past decade has been a
notable success story in cosmology. These standard candles offer us an
unparalleled opportunity of studying the cosmological expansion out to a
redshift of ~1.5. The consensus today appears to be that LCDM offers the best
explanation for the luminosity-distance relationship seen in these events.
However, a significant incompatibility is now emerging between the standard
model and other equally important observations, such as those of the cosmic
microwave background. LCDM does not provide an accurate representation of the
cosmological expansion at high redshifts (z>>2). It is therefore essential to
re-analyze the Type Ia supernova data in light of the cosmology (the R_h=ct
Universe) that best represents the Universe's dynamical evolution at early
times. In this paper, we directly compare the distance-relationship in LCDM
with that predicted by R_h=ct, and each with the Union2.1 sample, and show that
the two theories produce virtually indistinguishable profiles, though the fit
with R_h=ct has not yet been optimized. This is because the data cannot be
determined independently of the assumed cosmology---the supernova luminosities
must be evaluated by optimizing 4 parameters simultaneously with those in the
adopted model. This renders the data compliant to the underlying theory, so the
m odel-dependent data reduction should not be ignored in any comparative
analysis between competing cosmologies. In this paper, we use R_h=ct to fit the
data reduced with LCDM, and though quite promising, the match is not perfect.
An even better fit would result with an optimization of the data using R_h=ct
from the beginning.
