The positive trend among the homework scores and the test scores would reveal that if a student does well in homework, he is likely to do well in exams. This can be explained in the sense that the homework will serve as the practice for the student before finally taking the exam.
A positive slope of the trend line comparing homework scores and test scores means that higher homework scores infer a higher test score. A strong relationship between the two is a good predictor of a relationship between homework scores and test scores.
