I made a recruitment error by scheduling an interview with a participant who isn't fit for my study. What is the appropriate protocol for canceling an interview?
If you can reach the person prior to 24 hours before the study, then just contact them to cancel. No big deal.
If not, you might think about paying them some portion of the compensation they would have received.
And, of course, thank them and keep them in mind for future studies (if they might fit into another one).