  We studied the statistical properties of the luminosity distance and internal
extinction data of type Ia supernovae in the lists published by Tonry et al.
(2003) and Barris et al. (2004). After selecting the luminosity distance in an
empty Universe as a reference level we divided the sample into low $z<0.25$ and
high $z \ge 0.25$ parts. We further divided these subsamples by the median of
the internal extinction. Performing sign tests using the standardized residuals
between the estimated logarithmic luminosity distances and those of an empty
universe, on the four subsamples separately, we recognized that the residuals
were distributed symmetrically in the low redshift region, independently from
the internal extinction. On the contrary, the low extinction part of the data
of $z \ge 0.25$ clearly showed an excess of the points with respect to an empty
Universe which was not the case in the high extinction region. This diversity
pointed to an interrelation between the estimated luminosity distance and
internal extinction. To characterize quantitatively this interrelation we
introduced a hidden variable making use of the technics of factor analysis.
After subtracting that part of the residual which was explained by the
hiddenmaking use of the technics of factor analysis. After subtracting that
part of the residual which was explained by the hidden variable we obtained
luminosity distances which were already free from interrelation with internal
extinction. Fitting the corrected luminosity distances with cosmological models
we concluded that the SN Ia data alone did not exclude the possibility of the
$\Lambda=0$ solution.
