Data Analysis with R, Second Edition - Second Edition

A word of warning

Before we move on, a word of warning: the first part of every regression analysis should be to plot the relevant data. To convince you of this, consider Anscombe's quartet depicted in the following figure:

Figure 9.6: Four datasets with identical means, standard deviations, regression coefficients, and R²

Anscombe's quartet holds four x-y pairs that have the same mean, standard deviation, correlation coefficients, linear regression coefficients, and R²s. In spite of these similarities, all four of these data pairs are very different. It is a warning to not blindly apply statistics on data that you haven't visualized. It is ...