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Arellano-Bond test for AR(1) in first differences: z =  -3.44  Pr > z =  0.001
Arellano-Bond test for AR(2) in first differences: z =  -0.43  Pr > z =  0.664
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Arellano-Bond test for AR(2) in first differences: z =  -0.43  Pr > z =  0.664 怎么看是否相关，原假设是什么，pr值大于多少才算不相关