Which of the following is considered a less serious complaint resolution method?

A letter of reprimand is considered a less serious complaint resolution method because it serves as a formal, yet often private form of discipline. It typically represents a warning to the individual regarding their behavior or actions without imposing harsher penalties. This method is aimed at correcting behavior through communication rather than through punitive measures.

In this context, the other options represent more severe forms of complaint resolution. An advisory note, while it might seem lighter, typically provides guidance rather than reprimand but can still imply ongoing oversight. An administrative penalty generally involves monetary fines or other costs imposed due to a violation, indicating a stronger consequence for misconduct. A hearing is a formal legal process that can lead to serious sanctions and indicates that the situation is being taken very seriously.

Thus, a letter of reprimand functions primarily as a corrective tool rather than a punitive one, which is why it is classified as a less serious method of resolving complaints.