• Corpus ID: 124421936

THE RELIABILITY OF MEASURING INSTRUMENTS

@inproceedings{Knapp2009THERO,
  title={THE RELIABILITY OF MEASURING INSTRUMENTS},
  author={Thomas R. Knapp},
  year={2009}
}

• T. R. Knapp
• Published 2009
• Psychology

The goal of publishing this text in the Edgeworth Series is to provide a free resource for educational and research purposes. Preface Can you say "reliability" without saying "validity"? (Can you say "Rosencrantz" without saying "Guildenstern"?) I hope so, because this book is all about reliability, except for a brief appendix in which I discuss validity and for occasional comments in the text proper regarding the difference between reliability and validity. But isn't validity more important than reliability? Of course; a reliable instrument that doesn't measure what you want it to measure is essentially worthless. The problem is that the validity of a measurement device ultimately relies on the subjective judgment of experts in the field (all of the current emphasis on construct validity to the contrary notwithstanding), and my primary purpose in writing this book is to pursue those statistical features of measuring instruments that tell you whether or not, or to what extent, such instruments are consistent. There are 11 chapters in the book. Chapter 1 is an introductory treatment of the concept of reliability, with special attention given to its many synonyms and nuances. The following chapter addresses the associated concept of measurement error, with an extended discussion of "randomness". Chapter 3 is devoted to reliability theory and is the most technical section of the book, but if you think back to your high school mathematics you will recognize the similarity to plane geometry, with its counterpart definitions, axioms, and theorems. (It is assumed that you are also familiar with descriptive statistics such as means, variances, and correlation coefficients, and with the basic principles of inferential statistics.) Chapters 4 and 5 treat, respectively, the concept of attenuation and the interpretation of individual measurements. In Chapter 6 I try to summarize the literature regarding the reliability of difference scores of various types and the controversies concerning some of those types. The matter of the reliability of individual test items is explored in Chapter 7. Discussion of the internal consistency reliability of the total score on a test that consists of more than one item (the usual case) follows naturally in Chapter 8, where the primary emphasis is on Cronbach's alpha (coefficient alpha). Chapter 9 is concerned with statistical inferences from samples of "measurees" to populations of "measurees". In Chapter 10 I try to bring everything together by applying reliability theory to a set of data that were generated …