phenol compounds and carbonic acid derivatives for example one important polycarbonate melt polycarbonate may be prepared via the melt polymerization of diphenyl carbonate and bisphenol a bpa the reaction is conducted at high temperatures allowing the starting monomers and product to remain molten while the reactor pressure is staged in order to more effectively remove phenol the by product of the polycondensation reaction during the melt polycarbonate manufacturing process data may be collected via sensors in order to monitor process performance using this collected information the relative importance of various process variables x i may be determined and an inference model may be developed to predict such outcomes as fries concentration pellet intrinsic viscosity iv melt polycarbonate grade and other product parameters further process variables x i causing abnormal performance may be detected and identified as a result a manufacturing plant staff may better understand process performance and make sound business decisions referring to fig1 a multivariate statistical process analysis mspa method 10 for the consistent production of melt polycarbonate begins with the collection of sensor data over a predetermined period of time 12 for example data from one melt polycarbonate manufacturing plant included information about process variables x i and product variables y i from about 343 polymerization runs for each polymerization run process variables x i and product variables y i were recorded once a list of process variables x i and product variables y i used for multivariate analysis is presented in table 1 in the above table u201c r 3 u201d and u201c r 4 u201d refer to specific polymerization stages within the physical melt polycarbonate manufacturing system an exemplary description of such polymerization stages is presented in international.