A group of students were followed over time to determine their quality of college life. The Quality of Life Index was used to rate the student's perceptions on a scale of 1 - 7 (with '1' representing poor quality of college life, and '7' representing an excellent quality of college life). The instrument was given to the study group at the beginning of each year until they graduated. Which test would be best to analyze these data?

A. Spearman Rho rank order correlation

B. Kruskal-Wallis test

C. Friedman Test

D. Phi coefficient