Thank you all. I do have copies of the school's books and it's not in there either. I've just been in contact with his gifted teacher to request the supplemental material the classroom teachers are using.

Our DS is a public school student who is using AoPS pre-algebra as a complete course replacement for his PS math curriculum. We are in the process of working with our district to gain approval to do the same next year with Algebra. However, we live in PA where Algebra is a Keystone exam course (required for graduation) and he will be required to sit for it as well as the grade level PSSA exams. During the AoPS curriculum review, the following statistical topics are not included in AoPS but will be required for our PSSA and Keystone exams, so we will need to provide supplemental material. I am looking for supplemental material that is presented at the level of AoPS for the following: Scatter plots Line of Best Fit Correlation Regression Trend Interpolation Extrapolation After contacting AoPS, they directed me to this board and indicated that you may be of assistance offering suggestions. Thank you in advance for you help!