The difference in volume of 166 semen samples estimated by weighing the collection vessel and that measured by aspiration into a pipette (•) or decanting into a graduated cylinder () plotted against the mean volumes from the two compared methods (abscissa). The cylinder data presented are only those for ejaculate volume collected directly into the collection vessel (n = 27) but only one tenth of the pipette data are shown for clarity (every tenth datum from the list ordered in increasing weight-volume difference, N = 138).