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Screensize: 640 x 480 800 x 600 1024 x 768 1280 x 1024 UserName: Password: Anti-Spam Code: Format Mode: Basic  Help  Prompt  Format: Font Andale Mono Arial Arial Black Book Antiqua Century Gothic Comic Sans MS Courier New Georgia Impact Lucida Console Script MT Bold Stencil Tahoma Times New Roman Trebuchet MS Verdana   Size 1 2 3 4 5 6   Color Black Red Yellow Pink Green Orange Purple Blue Beige Brown Teal Navy Maroon LimeGreen Message: * HTML is OFF * Forum Code is ON Smilies [quote][i]Originally posted by erickzhou[/i] [br]Origin Ver 8. and Service Release (Select Help-->About Origin): Operating System: WinXP First question: I have fitted my data by 2-D polynomial surface, and the "Adj. R-Square" is 0.92173. However, I don't know well about the equation to get adjusted R-square error. The equation is R^2=1-(Rss/dferror)/(Tss/dftotal), I don't know the meaning of dferror and dftotal. Can you give me some explationations and references. The detailed information of this equation can be found in the chapter of "goodness of fit" (http://www.originlab.com/www/helponline/Origin/en/UserGuide/Goodness_of_Fit.html). Second question: In the chapter of "Graphic Residual Analysis" (http://www.originlab.com/www/helponline/Origin/en/UserGuide/Graphic_Residual_Analysis.html), the residual vs. independent plot was given for the case of curve fitting. However, no quantitive results was given about residual analysis, they only told me to judge from the plots. Furthermore, in the chapter of "Interpreting results" of the reference of "Marko Ledvij. Curve Fitting Made Easy."(The Industrial Physicist. Apr./May 2003. 9:24-27.), residual analysis was not used to expalin how well the model fits the data. From above information, can I say that if I have already known the true model of my data, the "Adj. R-Square error" is enough for assessing the model. [/quote]   Check here to include your profile signature. Check here to subscribe to this topic.