This revised and updated volume describes methods which are now a fundamental part of the theory and explanation of data analysis. This edition includes numerous extensions and devices such as component and component-plus residual plots, cross-verification with a second sample and an index of required x-precision. The methods described have been applied to agricultural, environmental, management, marketing, medical, physical and social science studies. This work also provides a historical insight into how computer technology has come to be used in data processing and analysis.