A guidance counselor wanted to know if anxiety differs based on time (first day of class in relation to the last day of class), and if this differs based on year in school (as a freshman, sophomore, junior, or senior). She collected data on a single group of students across their entire high school career at these eight time points first and last day of freshman, sophomore, junior, and senior year. Anxiety was measured using a standardized scale ranging from 0 50, with higher scores indicating greater anxiety. Question: What is the most appropriate statistical test to conduct given this scenario?