This book is designed as a laboratory companion, student textbook or reference book for professional scientists. The text is for use in one-term numerical analysis, data and error analysis, or computer methods courses, or for laboratory use. It is for the sophomore-junior level, and calculus is a prerequisite. The book provides an introduction to the techniques of data analysis and error reduction. Monte Carlo simulations have been added to this new edition to help students plan experiments and evaluate the statistical significance of results. A new section on cubic splines and their application to curve plotting has also been added and examples have been updated and are now written in Turbo Pascal. Problem sheets at the end of each chapter have been expanded to include exercises that range in complexity from simple statistical calculations to short projects. Computer routines are more detailed and complex, reflecting the stronger computing skills of today's students. Sample programs are provided in an appendix and on IBM diskettes to accommodate the increased complexity of the routines.