Abstract
This book is based on the principle that it is important to understand what you can do before you learn to measure how well you seem to have done it. The book is about explorating data analysis, about looking at data to see what it seems to say. It concentrates on simple arithmetic and easy-to-draw pictures. It regards whatever appearances we have recognized as partial descriptions, and tries to look beneath them for new insights. Its concern is with appearance, not with confirmation.