Hi Sujit,
Anand is right as I also feel that there must me something missing in your setup, if this is first time you are trying to implement SPC functionality.
Please can you also check if you have maintained Sampling Procedure => Valuation Mode as 'SPC Inspection" as suggested by Do-Wook Kim in the thread http://scn.sap.com/thread/2138475?
Thanks,
Arijit