Depending on the problem representation
and operator, one may wish to consider an alternative
definition of genetic dissimilarity, such as the distance from the
mean of only one standard
deviation. Next, the the original fitness
definition for outliers is used, but the genetic difference will now be based
on **o**ne standard deviation.
This change should allow more individuals to be considered as
*dissimilar*.

Figure 7.6 shows the same plots
as above for the number of outliers and the ratios of selection and
survivability, but now using the one standard deviation criterion.
Here, one can see again how a slight increase in the number of
outliers
causes their selection and survival rates to increase.
The right plot of this figure emphasises
the large spikes of the survival ratio of outliers.
In contrast to Figure 7.5, the survivability
of outliers, while still unstable, tends to decrease during the
evolutionary process.
The in-lier survivability frequently intersects the selected ratio,
while
the un-fit individuals tend to have lower survived ratios compared
to the selected ratio.
These results show that as the population loses diversity and
becomes genetically converged, the outlier survivability becomes
more unstable.
When the number of outliers are high enough to be selected,
they produce children with high survivability, but
at an increasingly varied rate
during the course of the run.
This *view* of outliers, compared with Figure 7.5,
shows that outliers, which have a dissimilarity between 1 and 2 standard
deviations from the population's mean, play a more important role
initially in search. As Figure 7.5 shows outliers
with a dissimilarity greater than 2 standard deviations,
Figure 7.6 confirms that the addition of
outliers with a dissimilarity greater than 1 and less than 2 standard
deviations account for this increased dissimilarity.
However, in the later stages of the evolutionary process, the outliers
have a lower survivability.

Finally, the above two methods are combined to define an outlier as
being one standard deviation from the mean average pair-wise edit
distance and being better-than or equivalent-to half the population in
fitness. Figure 7.7 shows that
when the outlier class is made larger by including equivalent
fitness and only being one standard deviation from the pair-wise
distance mean, the survivability rate of outliers is consistently higher
than its selection rate, but still unstable.
This *view* of outliers, combined with Figures 7.4 and
7.5, shows clearly how the population converges
to be mostly equivalent and genetically similar. Also, Figure
7.7 shows that when outliers are
viewed using the equivalent fitness criterion, their survivability
is higher for longer periods.