This is the default selection. It assumes that the random errors are heteroscedastic (have non-constant variance) and estimates the regression coefficients by weighted least squares, where weights at each point are:
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For model y = xb
w = 1/v, where v is the square of the std dev that has been input for that point.
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For model ln (y) = xb
w = (y2)/v, where y2 is the square of the response for that point and v is the square of the std dev that has been input for that point. (Motivated by delta method.)