1. A method for performing management and diagnostic functions in an advanced process control (APC) system, the method comprising: providing a cloud computing system communicatively coupled by a first communication device to at least one APC control computer; said cloud computing system including an APC management computer having a first processor connected to a first storage device having a first non-transitory machine-readable storage medium storing a data collection module and a step testing module and said APC management computer is programmed to implement said data collection module and said step testing module causing said APC management computer to execute: retrieving operating process data from said APC control computer; performing an iterative step test on said APC system, wherein said iterative step test modifies at least one test parameter of said operating process data and identifies changes to a set of remaining parameters of said operating process data resulting from modification of said test parameter; determining at least one process variable from said iterative step test; generating at least one process model based on said process variable, and transmitting said process model to said APC control computer.