As you read the text, not only should you be working through the examples by hand and with the software, but you should also be taking notes to help you remember and understand what you have read. Here is one technique for analyzing written material and making sense out of it for you. This will help you in reading material like this, but will also help you to learn how to write material like this for yourself.
It may help to separate each section into paragrphs, then describe each of these paragraphs with two different words or phrases. The first word could refer to the content of the paragraph; for example, it might be about variables or about observational data. The second word should refer to the purpose of the paragraph in the overall document; for example, is it an introduction or a clarification? Some other possible purposes for a paragraph are ”definitions”, ”examples”, ”exceptions”, ”conclusions”, and ”summaries”. There are many more possibilities. The point here is not to get the ”right answer” but to come to some understanding on your own. You may be asked to discuss this in class.