记不清是不是了，好像x11过程和x12过程的结果是带了检验季节性的，你可以去看看详细的SAS help

Combine your data into monthly format and plot it against time to see if there similar sale patterns in the SAME month, for example sales is down in Jul, Aug and up in Jan, Feb. This may identify seasonality.

Or plug a 11 month dummy variables in a regression. The T and F tests should give you a clue whether these is an evidence of seasonality.