Research:Estimating session duration
Session duration represents the amount of time a user spent active during an activity session under the assumption that, in between a users actions, he/she is engaged, and therefore, duration and engaged hours can be estimate by measuring the time taken to complete the session.
Last edit - First edit
A naive way to derive session duration from an edit session is to simply find the difference in time between the first and last edits in the session. However, this approach does not account for the amount of time that the first edit in a session required to make, and therefore, sessions that contain only one edit would appear to have required zero labor-hours.
First edit padding
A method to account for the the time that the first edit took to complete is to add an additional amount of padding based on an estimate for the amount of time that the first edit out to have taken.
duration = (last_edit - first_edit) + padding
A method to generate a reasonable padding value is to calculate the average time between activities across sessions that contain more than one activity, (430 seconds for Wikipedia edits in April of 2012). By combining this mean inter-activity time with the difference in time between the first and last session activities one can produce an estimated session duration that accounts for the necessary work for producing the first edit.
duration = (last_edit - first_edit) + 430 seconds