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s_b2
2010 Aug 05
2
compare gam fits
...uncertainty of this function (e.g. computing the confidence
interval of the difference at each value of C).
One thought is that predict.gam(...,se.fit=T) returns SE values, so if
I could find out the N on which these SE values are computed, I could
compute the difference CI as
sqrt( ( (SD_B1)^2 + (SD_B2)^2 ) / N ) * qt( .975, df=N-1 )
However, I can't seem to figure out what value of N was used to
compute the SEs that predict.gam(...,se.fit=T) produces. Can anyone
point me to where I might find N?
Further, is N-1 the proper df for the call to qt()?
Finally, with a smooth function and 95% co...