(Please note that this is all hypothetical at this point and the data specifics should not matter that much).
Let's say I have a dataset where participants took a certain amount of time to complete a task (x-axis below). These participants naturally separated into two rough groups: those who took about 4 seconds and those who took about 11 seconds. If I want to label participants as either "slow" or "fast", how could I reasonably do this? What is this sort of binning called? What papers should I start with reading? etc.
For the purpose of this question, assume the grouping is meaningful and I have a good idea of what caused it.