**3.3 Sampling Correction**

The groups used in the calibration are all small nearby groups with the following mean luminosity function:

M < _{G} | -19 | -18 | -17 | -16 |

(M
_{G}) | 1.3 | 3.2 | 4.5 | 6.4. |

In larger groups, a size of sample correction is required since the
larger the sample (population of group) the greater the probability of
occurance of outstanding objects. The correction was determined
through a comparison of the distance moduli derived for the
Virgo cluster taken as a whole or divided into
smaller groups and
subgroups. If *N*_{18} is the number of galaxies having
*M _{G}* < - 18 in a
group, the correction to the modulus derived as explained in
Sections 3.1 and 3.2
above is

*µ* = 2.0 (log
*N*_{18} - 0.5).