I've run a random vibration on an assembly, then reviewed both the von Mises RMS stress plot and a graph of the von Mises PSD stress (psi^2/Hz) vs frequency.  When I calculate the RMS value of the area under the curve, my values correlate to the RMS stress plot in Solidworks (approximately 28 psi).  However, when I right-click on Results and List Stress displaying the von Mises stress at a plot step in the middle of my PSD curve I get a max von Mises stress of 3600 psi.  I'm not sure what this value is exactly and how it is so much different from the other values.  I wouldn't expect it to be exact since it is taken at a discrete frequency, but how can it be so much larger?  Any help would be greatly appreciated.