The invention relates to a method for monitoring a manufacturing process, which by using a linear combination of measured variables with judiciously chosen weighting, produces a suitable (optimal) signal for determining each parameter. The extraction of the parameters from the measured variables is thus greatly simplified and in many cases becomes actually possible for the first time. According to the invention, large amounts of data may now be prepared, such that the crucial information (parameters) can be obtained from the data, almost in real time, or in real time.