Changes to Standard Deviation Report

Although I now understand that the shaded gray area represents 1 standard deviation from the mean, one key feature that would greatly enhance the usefulness of this Report would be a checkbox or some option that would exclude scores of "0". The mean and standard deviation are greatly affected and the curve is skewed by zeroes, and since those scores wouldn't matter to us in this kind of analysis, we would rather leave them out of the calculations and look at only those students who completed the assignment.