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3.3 Sampling Correction

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

MG < -19 -18 -17 -16
Nbar (MG) 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 N18 is the number of galaxies having MG < - 18 in a group, the correction to the modulus derived as explained in Sections 3.1 and 3.2 above is

Deltaµ = 2.0 (log N18 - 0.5).