An educator is interested in testing the hypothesis that student knowledge changes over the course of the summer. To test this hypothesis, they give a knowledge comprehension test to 9 students at the conclusion of their year in second grade. Those same students are then tested with a different exam of similar difficulty and knowledge base at the end of the summer, just before they begin third grade. The data for this experiment can be found in the file on blackboard labeled for "Student Knowledge study".

Using an alpha of 0.05, what is the critical value?