Without knowing the process, it sounds as if you want to compare the users. A Box Plot is a good option which would require you to create a column of data for each user. Perhaps you’d be collecting the volume by day (each row is a day)? Another option would be to total the volume for each user for a set time period and then put those users and their totals into a table to create a Pareto Chart. That won’t show the variation in volume, but it will give a clear picture of the user with the greatest volume. I hope that helps!