median. The other galaxies are too faint to be in the survey. RSCG 47, a group with $N = 4$ galaxies, is isolated according to Hickson’s criterion.

Because of the large scale structure in the redshift surveys, the distribution of groups with redshift is nonuniform and varies among the three portions of the survey. The median group redshifts for individual portions of the survey are: $z=0.007$ for CfAnorth, $z=0.017 $ for CfAsouth and $z=0.012$ for SSRS2.

Next, we explore the properties of the RSCG’s and compare them with the HCG’s. Although the selection algorithms for HCG’s and RSCG’s are not identical, the systems in the two catalogs have similar physical properties.

Membership Frequency
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Figure \[fig:freq\]a shows the frequency of occurrence of groups of all populations $N$ in our catalog (solid line) and in the HCG catalog (dashed line). The overall distributions do not match. Hickson only finds triplets when his groups selected on the sky contain interlopers; in other words, triplets are underrepresented relative to our sample. However, the match is excellent for groups with $N \geq 4$ (Figure \[fig:freq\]b), when the distribution is renormalized. Both distributions also agree with models of compact groups formed as subsystems within loose 