This section moves to a closer-grained account of instruments for collecting data, how they can be used, and how they can be constructed. We identify eight kinds of instrument for data collection in what follows, and have expanded on the previous edition of the book by new chapters on testing (including recent developments in item response theory and computer-adaptive testing), questionnaire design and observation, together with material on focus groups, statistical significance, multilevel modelling, laddering in personal constructs, telephone interviewing, and speech act theory (echoing elements of critical theory that were introduced in Part One).
The intention of this part is to enable researchers to decide on the most appropriate instruments for data collection, and to design such instruments. The strengths and weaknesses of these instruments are set out, so that decisions on their suitability avoid being arbitrary and the criterion of fitness for purpose is held high. To that end, the intention is to introduce underlying issues of principle in instrumentation as well as to ensure that practical guidelines are provided for researchers. For each instrument the purpose is to ensure that researchers can devise appropriate data collection instruments for themselves, and are aware of the capabilities of such instruments to provide useful and usable data.