Back to basics (22) - Least squares, statistics and all that

This is the nineth of a series of articles presenting some thoughts about L east Squares Statistics, Quality Control and other related matters, which m ay be of interest to students, or practitioners new to the particular appli cations described. The treatment is deliberately elementary and the example s are simplified so that the various concepts can be developed with clarity . Now and then, the editor will enter a word of caution in the text, where he feels that the treatment has been oversimplified or for other reasons. A s in previous articles, the topic is presented as a dialogue between this p ractising surveyor Nigel Atkinson and a retired academic Arthur Allan. The editor encourages comments as the series unfolds.