ABSTRACT
One of the most reliable sources of waffles in North America, if not the entire world, is a Waffle House diner. Waffle House is nearly always open, even just after a hurricane. Most diners invest in disaster preparedness, including having their own electrical generators. The truth is that correlation is not rare in nature, but rather very common. In large data sets, every pair of variables has a statistically discernible non-zero correlation. There's only one predictor variable, so a single scatterplot can convey a lot of information. With multivariate regression, one will need more plots. There is a huge literature detailing a variety of plotting techniques that all attempt to help one understand multiple linear regression. None of these techniques is suitable for all jobs, and most do not generalize beyond linear regression. A predictor variable residual is the average prediction error when people use all of the other predictor variables to model a predictor of interest.
