“…According to the experimental design approach, we can classify these variables into 2 types of factors: internal ones (load factor, number of passes, time per table, liter per table, basis weight, number of layers, number of products and drying time) and external ones (temperature, humidity, pressure). 2 factors (passes number and number of layers) are discrete ones that can each take 3 states and that are binarized (Thomas and Thomas 2009).…”