Paper is more focused on "feedback benefit learning" instead of how long should people wait for feedback. Seems that you are quoting another paper instead. But

Paper is more focused on "feedback benefit learning" instead of how long should people wait for feedback. Seems that you are quoting another paper instead. But I don't think it is definitive, as you see, n=27. Also the experiment setting is not about how long after initial test, it is about how short before the next test. https://link.springer.com/article/10.3758/MC.37.8.1077 https://link.springer.com/article/10.3758/MC.37.8.1077 > The participants were 27 students enrolled in Grade 6 at The School at Columbia University in New York City.