I don't yet see a solution to the repeatability problem. While the
repeatability at each landmark can be assessed at each landmark, the ratio
of the repeatability to the biological variation at each landmark cannot be
calculated using any method I have seen. The work done in this area has
focussed on repeatability/biological-variation of shape variables (Arnqvist
& Martensson, 1998). The ratio is not calculated for any specific
landmarks. The landmarks are the measurements, so how can we know which of
our measurements are good and not-so-good?
Ben
----- Original Message -----
From: "morphmet" <[EMAIL PROTECTED]>
To: "morphmet" <[email protected]>
Sent: Thursday, July 21, 2005 12:17 PM
Subject: Re: Repeatability
>
> I'm a bit late in jumping on the repeatability bandwagon, but for what
> it's worth, regarding semilandmarks, allow me to throw in my ten cents'
> worth.
>
> Their initial positions along the outline are arbitrary, but I assume
> one could probably derive new coordinates for them after having "slid"
> them in TPSRelw, and then treat them as true landmarks for the purposes
> of repeatability.
>
> If one felt compelled to do so.
>
> That would, however, not be statistically valid since their final
> positions will be determined by the positions of those terminal
> landmarks which anchor them.
>
> Repeatability of the semilandmarks will therefore be related to
> repeatability of the terminal landmarks, and my personal feeling is to
> not worry about the semilandmarks too much, but take very special care
> in minimising digitising error in terminal landmarks.
>
> > Lets see, take a x number of individuals, make three repeated
> > measurements, preferably by different people, and estimate the
> > proportion of the variation that is explained by individual versus all
> > the available variation. Either landmark by landmakr, of all at once
> in
> > a MANOVA.
> >
> > For semi landmarks, no idea, never worked with those.
> >
> > Good luck.
> >
> > Kim
> >
> > morphmet wrote:
> >
> >> I was simply wondering what would be the best way, the most
> appropriate
> >> statistical test, to evaluate the repeatability of your landmark
> >> placement.
> >>
> >> Furthermore, would this method also work with semi-landmarks?
> >>
> >>
> >> Thanks
> >>
> >> Martin
> > --
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> >
> >
>
>
>
>
>
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