and three cv values cv 1m cv 10cm cv 3cm are calculated as quality characterizing magnitudes in a similar manner the measuring member 9 in the sliver guide 6 takes thickness measurements of a determined length of the undrafted sliver 5 and from these measured magnitudes quality characterizing cv values cv in are calculated the determination of the cv values occurs preferably for four application points of regulation r expediently in each instance two application points of regulations r are selected on the one side and two application points of regulation r are selected on the other side of the optimal application point of regulation r opt in each instance a quality characterizing number qk is determined by calculation from the cv values of the un drafted sliver 5 and the drafted sliver 5 u2032 u2033 further a function between the numbers qk and the corresponding application points of regulation r are calculated in the computer 26 and displayed on the screen 27 fig3 and 4 a polynomial of the second degree is determined from the four values of the application point of regulation r and the respective quality characterizing numbers qk and subsequently the minimum of the curve is calculated the minimum point of the function corresponds to the optimum application point.