Dear list members,
I am fitting occupancy models in MARK and when I look at the variance-covariance matrix I got negative variances (diagonal). Is that possible?
Thank you very much in advance.
Best,
Manuel Spínola
Negative variance
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Negative variance
by mspinola » Mon Jun 01, 2009 5:59 am
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Negative variance
by gwhite » Mon Jun 01, 2009 3:34 pm
Manuel:
No, you cannot have negative variances. I suspect you are not actually looking at the VC matrix correctly. If the variances are actually negative, then the SE will be zero in the output. Is this the case?
If the SE are zero, then I would like to see the MARK DBF and FPT files that have this output!
Gary
No, you cannot have negative variances. I suspect you are not actually looking at the VC matrix correctly. If the variances are actually negative, then the SE will be zero in the output. Is this the case?
If the SE are zero, then I would like to see the MARK DBF and FPT files that have this output!
Gary
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Negative variance
by Paul Lukacs » Mon Jun 01, 2009 3:59 pm
I recently (today) got negative variances from the occupancy models. It was due to opening a file created in an older (~8 month old) version of Mark in a new version. Rerunning the models with the new version of Mark fixed the problem.
Paul
Paul
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