Question

Problem 9 (15 points) Professor Dunderhead teaches statistics every semester exactly the same way. Scores on his final exams are remarkably consistent, with mean score 76.4 and standard deviation 7.3. This semester the professor discovers he has mistakenly been drinking decaffeinated coffee for years and switches to caffeinated coffee. He finds that a random sample of 15 of his students earns an average score of 79.7 on the final. He wonders if this is sufficient evidence to conclude his students this semester performed differently on the final than in years past. (d) At the 5% level state your conclusion in words.