I have some data $X_1, X_2, ..., X_n$ which shows no apparent sign of linear drift. Nethertheless, I want to conduct some sort of test which I could use in instances which are not so clear.
Is there a way of testing this without assuming normality of error terms etc?
Perhaps a randomisation test of some sort?
My data in particular is measured every day for roughly 100 weeks. There was a weekly trend in the data which I have removed, and so now I have a time series centred at zero. I basically want some sort of test I can apply to data of this type with minimal assumptions that tests whether or not the data has some linear drift.