Dear Fish-folks,

I want to compare linear regressions (for example ln length - ln weigth)
with respect
to differences in slope and intercept. We have found several
complicate formulae in statistical textbooks. However, I know that one could use
also the ANOVA-approach - but how? I have intensively studied the manual of our
statistical software (Statistika), and have found that linear regression and
ANOVA are basically identical. Thus, it may be simple if we have similar
x-values
each year. But in practice, the fish lengths (x-values) are measured
independently each year,
that means the range of fish lengths and weights may vary. My idea was to group
the weigths of fish as dependent variables, and to use the lengths as
covariables,
and then to run an ANCOVA-procedure. But I could not identify whether this is
correct. Has anyone some experience with this topic?

Many thanks
Yours sincerely
Thomas
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Dr. Thomas Mehner
Institute of Hydrobiology
University of Technology
D-01062 Dresden
Germany

Tel.: (++49)(351) 463 2018
Fax:  (++49)(351) 463 7108
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