How Are the Peak Statistics Calculated in the Zetasizer Software?

Peak statistics available to users of the Zetasizer Nano software include the mean, mode, width, and area, all of which are calculated according to standard statistical procedures. For peaks that coalesce, the peak extent is defined to be the saddle point, and the statistics are then computed over this modified peak extent. Peak statistics are calculated using the expressions given below, where Yi is the Y axis value of the ith X axis class/bin and Xi is the X axis value in the center of the X axis class/bin. The figure below is provided for reference. Note, that peaks are numbered by order of the largest ordinate or Y axis value.



Area: Defined as the area under each peak, relative to the total area of the distribution



Mean: Defined as the average value of the peak, weighted by the Y axis parameter.



Mode: Defined as the center of the X axis class/bin with the largest Y axis value.

Width: Defined as the standard deviation of the peak.