Preface
Writing a dictionary of statistics is not many people’s idea of fun. And it wasn’t ours.
Can we say that we have changed our minds about this at all? No. Nevertheless, now
the reading and writing is over and those heavy books have gone back to the library,
we are glad that we wrote it. Otherwise we would have had to buy it. The dictionary
provides a valuable resource for students – and anyone else with too little time on
their hands to stack their shelves with scores of specialist statistics textbooks.
Writing a dictionary of statistics is one thing – writing a practical dictionary of sta-
tistics is another. The entries had to be useful, not merely accurate. Accuracy is not that
useful on its own. One aspect of the practicality of this dictionary is in facilitating the
learning of statistical techniques and concepts. The dictionary is not intended to stand
alone as a textbook – there are plenty of those. We hope that it will be more important
than that. Perhaps only the computer is more useful. Learning statistics is a complex
business. Inevitably, students at some stage need to supplement their textbook. A trip
to the library or the statistics lecturer’s office is daunting. Getting a statistics dictio-
nary from the shelf is the lesser evil. And just look at the statistics textbook next to it –
you probably outgrew its usefulness when you finished the first year at university.
Few readers, not even ourselves, will ever use all of the entries in this dictionary.
That would be a bit like stamp collecting. Nevertheless, all of the important things are
here in a compact and accessible form for when they are needed. No doubt there are
omissions but even The Collected Works of Shakespeare leaves out Pygmalion! Let us know
of any. And we are not so clever that we will not have made mistakes. Let us know if
you spot any of these too – modern publishing methods sometimes allow corrections
without a major reprint.
Many of the key terms used to describe statistical concepts are included as entries
elsewhere. Where we thought it useful we have suggested other entries that are
related to the entry that might be of interest by listing them at the end of the entry
under ‘See’ or ‘See also’. In the main body of the entry itself we have not drawn
attention to the terms that are covered elsewhere because we thought this could be
too distracting to many readers. If you are unfamiliar with a term we suggest you
look it up.
Many of the terms described will be found in introductory textbooks on statistics.
We suggest that if you want further information on a particular concept you look it up
in a textbook that is ready to hand. There are a large number of introductory statistics
texts that adequately discuss these terms and we would not want you to seek out a
particular text that we have selected that is not readily available to you. For the less
common terms we have recommended one or more sources for additional reading.
The authors and year of publication for these sources are given at the end of the entry
and full details of the sources are provided at the end of the book. As we have dis-
cussed some of these terms in texts that we have written, we have sometimes
recommended our own texts!
The key features of the dictionary are:
• Compact and detailed descriptions of key concepts.
• Basic mathematical concepts explained.
• Details of procedures for hand calculations if possible.
• Difficulty level matched to the nature of the entry: very fundamental concepts are
the most simply explained; more advanced statistics are given a slightly more
sophisticated treatment.
• Practical advice to help guide users through some of the difficulties of the applica-
tion of statistics.
• Exceptionally wide coverage and varied range of concepts, issues and procedures –
wider than any single textbook by far.
• Coverage of relevant research methods.
• Compatible with standard statistical packages.
• Extensive cross-referencing.
• Useful additional reading.
One good thing, we guess, is that since this statistics dictionary would be hard to dis-
tinguish from a two-author encyclopaedia of statistics, we will not need to write one
ourselves.
Duncan Cramer
Dennis Howitt