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using an appropriate transformation (see Zar, 1984) and again checked for normality
and homoscedasticity. One-way ANOVAs were then carried out together with a
Tukey test if significant. Weed effects were assessed by comparisons of weed
treatment plots with net plots. Although these could have been performed by Two-
sample t-tests, ANOVA tests together with a Tukey test were used so that the presence
of artefacts associated with the experiment could be determined, i.e., by comparisons
of the unmanipulated controls with net plots.
Pygospio elegans size-frequency distributions were compared between weed
treatment and control plots using the Kolmogorov-Smirnov (K-S) test and the chi-
squared (x 2) goodness of fit test. Both tests were used since although the former is
more appropriate for continuous data (Zar, 1984) the latter permits the identification
of those sizes contributing most to any significant differences. Size classes were
grouped so that no expected values were below 5 for the X2 test, as recommended by
Elliot (1977). All statistical analyses were performed using Minitab version 10.0
except the Kolmogorov-Smirnov test which was carried out by hand using the formula
for large sample sizes given by Smirnov (1948).
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