  Although individual observational groups vigorously test their data sets for
systematic errors, the pre-WMAP CMB observational data set has not yet been
collectively tested. Under the assumption that the concordance model is the
correct model, we have explored residuals of the observational data with
respect to this model to see if any patterns emerge that can be identified with
systematic errors. We found no significant trends associated with frequency,
frequency channels, calibration source, pointing uncertainty, instrument type,
platform and altitude. We did find some evidence at the ~ 1 to ~ 2 sigma level
for trends associated with angular scale (l range) and absolute galactic
latitude. The slope of the trend in galactic latitude is consistent with low
level galactic contamination. The residuals with respect to l may indicate that
the concordance model used here needs slight modification. See Griffiths &
Lineweaver (2003) for more detail.
