關於薪水(salary)與教育年數(educ)之間的關係究竟是不是線性， 相信大家看了殘差圖，都覺得兩者不是線性關係，而是二次關係 剛剛我設了教育年數的二次項（educ2）下去跑迴歸，發現Ra有不少的提高 我認為這樣應該比肉眼更可以證明 兩者不是線性關係， 附上資料，供大家參考。 regress salary educ educ2 Source | SS df MS Number of obs = 474 -------------+------------------------------ F( 2, 471) = 337.25 Model | 8.1208e+10 2 4.0604e+10 Prob > F = 0.0000 Residual | 5.6708e+10 471 120399257 R-squared = 0.5888 -------------+------------------------------ Adj R-squared = 0.5871 Total | 1.3792e+11 473 291578214 Root MSE = 10973 ------------------------------------------------------------------------------ salary | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- educ | -12428.48 1248.539 -9.95 0.000 -14881.88 -9975.088 educ2 | 612.9502 46.37833 13.22 0.000 521.8162 704.0843 _cons | 85438.24 8213.964 10.40 0.000 69297.69 101578.8 ------------------------------------------------------------------------------ regress salary educ Source | SS df MS Number of obs = 474 -------------+------------------------------ F( 1, 472) = 365.38 Model | 6.0178e+10 1 6.0178e+10 Prob > F = 0.0000 Residual | 7.7738e+10 472 164699741 R-squared = 0.4363 -------------+------------------------------ Adj R-squared = 0.4351 Total | 1.3792e+11 473 291578214 Root MSE = 12834 ------------------------------------------------------------------------------ salary | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- educ | 3909.907 204.547 19.11 0.000 3507.971 4311.842 _cons | -18331.18 2821.912 -6.50 0.000 -23876.24 -12786.1 --

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