Reporting on Absent Membres
Obtaining a list of members who did not attend an activity is a little tricky. If you run an activity report that includes attendance, it can only show members who did attend, not members who did not.
The solution is to run a membership report (like the Contact list, Roster, Directory, or any user-defined report based on membership data) and use a special criteria called "Absent from Activity".
This criteria set, used on the Contact List report in this case, will find any members aged 50+ who did not attend (were absent from) the "Boring Activity":
Don't try to use the Absent from Activity criteria on an Activity report, or no data will be found. Since an activity report can only show attending members, restricting it to members who aren't there will eliminate all attendees.