Dr. Fauci is testing new social distance guidelines designed to reduce the spread of Covid-19. The general population typically comes in close contact with an average of 60 people per day. He randomly assigns 30 participants to use social distance guidelines, and finds that they came into close contact with an average of 30 people per day, with a sample standard deviation of 10. He compares the "treated" sample to the "untreated" population, using a single-sample t-test (two-tailed, alpha = .05). What are the degrees of freedom