Re: Tyrannosaur eggs amd brooding

[tobin@cshl.org (Henry Tobin)]

>The null hypothesis, on phylogenetic basis, is that all dinosaurs used some
>degree of parental care, as both the in-group (birds) and the closest
>surviving outgroup (crocodillians) protect the nest and the young for some
>duration.
>
>
>Thomas R. Holtz, Jr.
>tholtz@geochange.er.usgs.gov
>Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
>U.S. Geological Survey                                FAX:      703-648-5420
>Branch of Paleontology & Stratigraphy
>MS 970 National Center
>Reston, VA  22092
>U.S.A.


I think I agree in spirit, but I believe that a more accurate statement for
statistical analyses would be to say that:

[1] Unless there is evidence to the contrary, when a member of a clade's
rating on a trait (such as degree of parental care) is unknown, its rating
should be assumed to be the mean of the other members of the clade (the
mean being the estimate which, over multiple cases, will differ least from
the actual rating than any other rating prediction).

[2] When a rating can be made on the basis of data, then this 'new' rating
of the previously unrated member can be compared to the clade as a whole to
see if it differs from the clade.  The null hypothesis says that there is
no difference between the control group (in this case, the member(s) of the
clade whose rating is previously, known) and the experimental group (the
member(s) whose rating is being compared to the ).  It is the 'burden' of
the analyzer (using a statistical test) to prove that this null hypothesis
is false, that is, that there really is a difference between the two
ratings.  Thus the null hypothesis is conventionally used as the starting
hypothesis when a test of differences is performed.


So statistically speaking, unless there is evidence to the contrary, it
should be predicted that T. rex  showed some degree of parental care
(estimable per [1] using data from previously rated members of the clade).


Henry Tobin

Beckman Neuroscience Center, Cold Spring Harbor Laboratory;
P. O. BOX 100, Cold Spring Harbor, NY  11724;
TELE: (516) 367-8886; FAX: (516); 367-8880; E-MAIL: tobin@cshl.org.