st: levin-lin-chu test in panel data

["Parul Chhabra" <parulchhabra@hotmail.com>]

Hello,
I am testing for the presence of a unit root in panel data using the 
levin-lin-chu test in stata. But i am not able to figure out which 
specification to consider(constant, constant and trend or no constant-no 
trend). I am getting a different result from all three of them. I would 
appreciate any help in this regard.
Thanks,
Parul

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