Query Regarding Unit Root Test

[sweetagarwal]

Hi...i have a question regarding ADF and PP test...
I am applying ADF test, I have 10 macro economic variables....out of which some of the variable i found stationary at level either on trend or on trend and intercept or both. whereas some i found stationary on first difference I(1) or on second differnce I(2).

So my first question is that should i take mix of levels and differences or should maintain uniformity i.e. if all the data is not found to be stationary at levels, i should take all the data in differences...

My second question is that when initially i plot graph, the data which found stationary at levels through ADF test is found non-stationary through graphical interpretation. What should i do for it?

Please answer my query.. thanks