Suppose you take a random sample of 20 students who are using a new algebra text which features group work and unit summaries and a second sample of 30 students who are using a more traditional text. You compare student achievement on the state test given to all students at the end of the course. Test whether new textbook improves student performance?

Below grade level At grade level Advanced

New text 8 6 6

Old text 6 15 9