  The Teerikorpi incompleteness bias in the distance modulus of a galaxy
cluster that is determined from incomplete data using the Tully-Fisher (TF)
method is discussed differently than has been done in earlier papers of this
series. A toy cluster is made with zero intrinsic TF dispersion but with slopes
that differ between the calibrators and the cluster data, showing the bias
caused by incorrect slopes. Intrinsic dispersion is added to the model and two
strategies are used to analyze the data; first by binning the data by line
width and then by apparent magnitude (the direct method), and second by binning
by magnitude and then summing over all line widths (the inverse method). To
illustrate these strategies, a composite cluster is made by combining the
observations of Virgo A and B subclusters with those for the Ursa Major I and
II clusters, corrected to the Virgo A distance. The cluster data are calibrated
using Cepheid distances to 25 galaxies that have adequate TF properties.
Different moduli calculated with varying completeness limits are displayed. The
cluster modulus derived from the complete cluster sample gives (m-M) = 31.42
+/- 0.2 (external) for Virgo A, 31.80 +/- 0.16 for Virgo B, 31.26 +/- 0.13 for
UMa I, and 31.58 +/- 0.17 for UMa II. Combining the Virgo A distance (D = 19.2
Mpc that has a range from 17.5 to 21.1 Mpc with its expansion velocity of 1175
+/- 50 km/s as tied to the remote kinematic frame gives a Hubble constant of
61km/s/Mpc with a range from 53 to 70.
