Values Residuals Resids. However, we have to keep in mind that this is just an example to get the idea across. We are not done until we have illustrated some use for the idea. Unlike art or pure mathematics, statistics is not an end in itself. There are some standard objections to using real data.
Many real studies are too complicated to use in an introductory course.
Many, but not all. Real data is messy, and we do not want our students to be so overwhelmed with the messiness that they miss the point currently under discussion. That is true, but we can find real data with all degrees of messiness. In addition, some messiness is essential if students are to have any hope of handling real data after our class is over. For too long, teachers of mathematics have given as a reason for studying Math.