This is a representation of the Chen Scale, used to measure entrustment in undergraduate medical education1.
The Chen Scale was first published in 2015 by Chen et al, in the context of allowable levels of supervision of a medical trainee performing an entrustable professional activity.
1 Chen HC, van den Broek WE, ten Cate O. The case for use of entrustable professional activities in undergraduate medical education. Acad Med. Apr 2015;90(4):431-6. doi:10.1097/ACM.0000000000000586