From:
Sukie Crandall
Date: 2001-08-31 18:10:00 UTC
Subject: deviation aspect -- on-set timing for adrenal growths
Just to explain about the most basics about slush factors in case a
few folks don't get that. In the study they had groups of on-set
ages in relation to how long before the altering had occurred. These
were NOT tightly clumped, at least for the most part (perhaps for
all, but I don't have the paper handy so am relying on memory).
That means that if you look at age A for neutering it is not defined
by a small age band years later in which adrenal growths appear, but
by a very diffuse blob. Look at age B for neutering and you imagine
that you will find another very diffuse blob for the on-set range.
If those two blobs have a wide range of OVER_LAP when adrenal growths
appear -- even with a few on the edge that don't) then the result is
that there is no real difference in on-set age range between age A
and age B -- until or unless later research clarifies or disproves
results. The few individuals on the edges may be different or they
could be just by chance, but for most there will not be a difference.
Now, say that age C's blob does not over-lap age A's or does so only
very slightly (or most are separated). Then you have a difference
that is discernable.
When a such factor is huge, trying to look at the difference between
two ages that are divided by a time frame smaller than the slush is
worthless.
Now, off-hand I can't recall what the +/- number was but I do recall
that it was HUGE and larger in either direction than the 6 month
increments in ages. If memory serves they later tried to run a line
through the means (averages) and form that arrived at about 3 and 1/2
years from neutering to onset of adrenal disease, BUT that was
actually something like 3 and 1/2 years PLUS OR MINUS 9 months
(though I seem to recall it being larger so even worse), If you look
at only the average and the slush factor then the RANGE seen for age
1 and 1/2 months at neutering is around 2 years and 10 and 1/2 months
to 4 years and 4 and 1/2 months, while the range for neutering at
age 6 months is from 3 years 3 months to around 4 years 4 and 1/2
months. Now, honestly, those of us who have had ferrets with later
adrenals know that the blob is even more diffuse.
You need to also look at the mode -- the FASHION, or most common age.
(Average is the ages added together and then divided by the total
number and that is the mean; median is the highest and lowest added
together and divided by 2.) If my memory serves the was about zip in
the way of tight clumping found so a person couldn't refine down to
the modes for two close age groups and see where those might differ.
Anyway, that is only a very most basic thing, but it's easy to
eye-ball to get a feel for what is going on before going further.