[R] joint confidence ellipsoid problem

[Christopher Fonnesbeck]

As the subject implies, I am trying to draw a joint confidence interval
of two variables, using the "ellipse" package.  However, the ellipse()
function plots an ellipsoid that is far too large than what I get when I
calculate the limits by hand. For the t option, I am using
sqrt(qf(level, df1, df2)) as I believe that I should be. I am giving a
variance-covariance matrix as the object argument. Anyone have a simple
idea of what may be going on? I would have to scale t by about 1/4 to
get it in the right neighbourhood.

Thanks in advance,
Chris Fonnesbeck
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Christopher J. Fonnesbeck 
Ph.D. Student

Georgia Co-operative Wildlife Unit
University of Georgia 
Athens, GA 30602

Email: cjf at fonnesbeck.net
Yahoo: fonnesbeck_chris

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