滞后期选择了12期，之前有120个样本，为什么到12期有几个样本量就变成了12个，求帮忙

Pairwise Granger Causality Tests
Date: 03/31/15   Time: 23:45
Sample: 2004M01 2015M12
Lags: 12










Null Hypothesis:
Obs
F-Statistic
Prob.








LIAV does not Granger Cause LOP
12
NA
NA
LOP does not Granger Cause LIAV
NA
NA








LCPI does not Granger Cause LOP
109
0.95045
0.5020
LOP does not Granger Cause LCPI
1.12225
0.3536








LM1 does not Granger Cause LOP
109
0.59067
0.8440
LOP does not Granger Cause LM1
1.56394
0.1182








LUR does not Granger Cause LOP
108
1.96868
0.0375
LOP does not Granger Cause LUR
1.23466
0.2740








LCPI does not Granger Cause LIAV
12
NA
NA
LIAV does not Granger Cause LCPI
NA
NA








LM1 does not Granger Cause LIAV
12
NA
NA
LIAV does not Granger Cause LM1
NA
NA








LUR does not Granger Cause LIAV
12
NA
NA
LIAV does not Granger Cause LUR
NA
NA








LM1 does not Granger Cause LCPI
109
0.59715
0.8387
LCPI does not Granger Cause LM1
2.37579
0.0109








LUR does not Granger Cause LCPI
108
0.76851
0.6806
LCPI does not Granger Cause LUR
1.26590
0.2544








LUR does not Granger Cause LM1
108
3.23585
0.0008
LM1 does not Granger Cause LUR
1.04682
0.4153