以下是对GDP的检验
Dickey-Fuller test for unit root Number of obs = 25
---------- Interpolated Dickey-Fuller ---------
Test 1% Critical 5% Critical 10% Critical
Statistic Value Value Value
Z(t) 12.192 -3.750 -3.000 -2.630
MacKinnon approximate p-value for Z(t) = 1.0000
以下是对GDP取对数的检验
Dickey-Fuller test for unit root Number of obs = 25
---------- Interpolated Dickey-Fuller ---------
Test 1% Critical 5% Critical 10% Critical
Statistic Value Value Value
Z(t) -1.618 -3.750 -3.000 -2.630
MacKinnon approximate p-value for Z(t) = 0.4739
按道理说两个结果应该都是有单位根的啊!怎么结果有差异呢?