Data-handling means the interpreting and refining of experimental results. This book is aimed at helping to improve confidence and skill in data-handling. It is intended for undergraduate students, and for graduate students who may still have a little to learn.

Although microbiology began with simple observations (the organisms are small, they have various shapes, and some are motile) the subject has become a quantitative, experimental science. As an example consider the following statement:

To reach this conclusion one must grow the organisms in a certain way, make weighings, extract the polymer, do a chemical assay, and then put all the information together in its proper order. None of these practical steps is difficult, but to achieve the final result, clarity of thought, rather than great mathematical ability, is definitely needed.

In recent times, the words ‘data-handling’ have taken on a second meaning, that is, the manipulation of very large quantities of data (such as DNA sequences) by using computer programs for analysis and comparison. This new big area of database management is not covered here. Everything in this book can be done with pencil and paper and a pocket calculator. That is by no means to decry computers; the whole of this text was written on a word processor, and all the figures have been drawn with Excel® or Corel Draw®.