Health Measurement Scales

Abstract

This book covers in detail how to develop a measurement scale: a questionnaire or instrument, with specific applications in health sciences. Its organization follows the steps developers will go through during the process beginning with how the individual items are developed, and the various biases that can affect responses (e.g., social desirability, yea-saying, framing). It then discusses different response options, such as Likert scales, adjectival scales, visual analogue scales, Harter scales, and face scales, and the advantages and disadvantages of each. The book then explains how to select the best items in the set, using various psychometric criteria; and how to combine the individual items into a scale. There is much discussion of reliability and validity, from both a theoretical and statistical perspective, with a separate chapter on generalizability theory. Although the perspective is that of classical test theory, there is also an in-depth presentation of item response theory. It concludes with a discussion of ethical issues that may be encountered in developing and using scales; and presents guidelines for reporting the results of the scale development process. In the appendices there is a comprehensive guide to finding existing scales, and a brief introduction to exploratory and confirmatory factor analysis.