DATA 606 Presentation

(a) Based on these graphs, which of the two exams has the strongest correlation with the final exam grade? Explain.

The strongest correlation is between Exam 2 and the Final (plot 2). We can see that although there is a direct relationship in both instances, the scores for Exam 2 are more evenly distributed along the linear model. Additionally, there is less variation in plot 2 – the average distance between each of the scores and the linear model is closer than those from the Exam 1 scores and the linear model.

(b) Can you think of a reason why the correlation between the exam you chose in part (a) and the final exam is higher?

Some reasons why the second exam was more correlated could be:

• High scores on first exam, low scores on final: The material in Exam 1 was introductory, so many individuals did very well. Since the final encompasses more than just intro material, individuals may have done worse on it.
• Less variation between Final and Exam 2: Exam 2 could have been more representative of the final. In other words, the same material could have been on both, so we would expect the scores to be similar.