Thanks, Matt. That clarifies a few things...in particular, I found the example you gave (quoted below) to be quite helpful. --Scott Calvin Sarah Lawrence College At 12:16 PM 3/1/2004 -0600, you wrote:

This is probably a bit off-topic from the original question (where I'd guess self-absorption to be the main issue,....), but let's consider typical fit results: S02= 0.9 +/- 0.1, sigma2= 0.015 +/- 0.005, and a correlation between S02 and sigma2 C_S02_sigma2= +0.90. One could conclude from these that a true value of S02= 1.0 was reasonable. But in order to get to S02= 1.0, sigma2 has to go up to ~= 0.019 (~= sigma2_best + C_S02_sigma2 * delta_sigma2). S02= 0.80 is also reasonable, but this implies sigma2 would drop to around 0.011. The correlation means that, although having either S02= 0.80 OR sigma2= 0.020 would be reasonable,t having both S02= 0.80 AND sigma2= 0.020 is much less likely.

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--Matt