st: negative and positive maximum likelihood ratios

[dspady@ualberta.ca]

Can someone please tell me what the difference is between a negative  
and a positive maximum likelihood ratio.  My intuition tells me that a  
'negative' MLR is one that is less than 1 and a 'positive' MLR is  
greater than 1 but I cannot find anything that describes these terms.
  As a second request: how does one calculate these ratios when doing  
logistic regression.  I know that you can test the ratios using lrtest  
but how can one actually calculate the ratio.
  Many thanks in advance.

Don Spady
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