VAR模型中的VAR lag extension Wald test的含义

根据下表的输出结果，应该如何确定滞后期呢？看joint的P值么？P<0.05时，DF是什么意思呢？

	DLZHX	Joint
Lag 1	3.462089817	3.462089817
	[ 0.062791]	[ 0.062791]
Lag 2	4.461601657	4.461601657
	[ 0.034665]	[ 0.034665]
Lag 3	0.205614566	0.205614566
	[ 0.650227]	[ 0.650227]
Lag 4	0.300859987	0.300859987
	[ 0.583344]	[ 0.583344]
Lag 5	0.439356441	0.439356441
	[ 0.507433]	[ 0.507433]
Df	1	1