No matter what stage of research you are in, if there is a quantitative element to it, buy, read, mark, learn and inwardly digest this book. I wish I had had it earlier in my research - as it is, it was remarkably important.

There are bits of it that may not be of use to particular researchers; however, the section on forumating the Central Research Question is very good indeed. (The book suffers, however, from jargon-itis, and a descent into the realms of abbreviations-r-us).