size: 5036KB - Crocodile Specialist Group

1'l
(ii) Linear regressron.
same rate throughout their Iives,
growth by a straight I ine. Their
ably bad:
crocodiles dontt qrow at the
so itrs silly to rnodel their
fit to TEST data r^ras predict-
RANK BASED LINEAR ALL LINEAR I,AST
ON:
hedian 9.5 g.s
hean I 9
Table 9: Linear Regression, Rank Out of 12
(iii) Von Bertalanffy fit by finite difference rnethods.
ll9Jel': -!r98_2)
s-uggests that using finear ieqression to
esErhate von Bertalanffy paraneters should be avoided if a non_
rhear: curve-fltting p_rogran is available. That is certainly
Erue tor our workl The fit of such curves to our TEST data
sets is alrnost uniformly terrible:
RANK BASED
ON:
median
mean
VONB FD ALL
9.5
l1
VONB FD I"AST
a2
I2
Iable 10: Von Bert., Finite Difference, Rank Out of t2
b. Alnost-decent options.
Quadratic regressions fit the CALfBRATION data sets
rarrly crgntly, and they usually perforn alnost as well on the
[E5 r OaEa SeLS:
RANK BASED
ON:
rnedian
nean
QUAD ALL
QUAD I,AST
Table 11: euadratic Equation, Rank Out of 12
Thus ve rnight conclude that
-quadratic equations do a prercy
good job of describing crocodlle grolrth. oa;""r;; there ts
one severe problern because the quadratic (= parabolic) equa_
tlons nust not be extrapolated to very ota aniriats-- unless one
assumes that some very serious crocodile shrinking is going on!