The probable source for OOT may be due to the following reasons: Sampling error i.e. not a uniform or representative batch sample, Analyst errors such as STD or sample weighing error, dilution error, wrong sample selection, improper sample handling, STP is not followed properly, Instrument or equipment errors & calibration error, inappropriate packing, storage condition is not proper, change in the vendor or lot number of crucial raw materials, errors during the manufacturing process and SOP was not followed accurately.