A survey of several hundred students at the same university asked students to report the number of credits they were taking and their SAT scores. The fitted line plot on the left regresses Math SAT on credits for all the students in the sample; the one in the middle is for the regression using full-time students only (12 or more credits); the one on the right is for part-time students only (less than 12 credits). The correlation and P-value are, respectively, r = + 0.12, P-value = 0.017 for all students together; r = + 0.07, P-value = 0.19 for full-time students only; r = + 0.17, P-value = 0.745 for part-time students only.
Write a paragraph or two discussing the relationship (if any) between number of credits and Math SAT score for the population of students from which the sample originated. Be sure to mention strength of relationship, strength of evidence, and possible confounding of variables.