Reliability concepts and methods: special focus section.

No matter the area of science, fundamental concepts are inexorably linked with instrumentation used to obtain measurements of them. In nursing science (Ventura, Hinshaw, & Atwood, 1981) as in all sciences, measurements should be faithful representations of characteristics of interest that gauge quantity with minimal error and enable examination of relationships and testing of hypotheses arising from theory and past research findings. Thus, accurate, precise measurement is the bedrock of all scientific endeavors, and advances in understanding are often preceded by and result from advances in measuring techniques. The basics of measurement science are the same across the disciplines, with variations and extensions reflecting the nature of the subject matter. Many critical constructs in nursing science are in the biobehavioral and psychosocial realms. Measurements are often obtained using self (patient)-report. Proxy reports (about child health status, obtained from parents; about patient status, obtained fromnurses) and direct observation of health-related behaviors (from carefully trained researchers) are also used. All these practices rely on psychometric principles, concepts, and methods—especially those related to reliability (repeatability) of measurements. Use of self-report on a single occasion is pervasive in nursing research (and research in related health sciences), and Cronbach’s alpha (Cronbach, 1951) is often regarded as “the” way to report reliability. Rules of thumb are invoked to determine whether reliability is “adequate.” These habits point out gaps in design of measurement studies and limited consideration of advances in psychometrics that, if used,would enhance quality of instrumentation—and minimize error in measurement that is an impediment to advancing nursing science. In his Presidential Address to the Psychometric Society, Prof. Klaas Sijtsma (2012) considered the future of psychometrics and asked “what can psychometrics do for psychology?” He extended his commitment to linking advances in psychometric theory and methods with substantive scientific areas when he suggested a series of papers on reliability forNursing Research. The resulting “Reliability Concepts and Methods” Special Focus Section in this issue of Nursing Research is a moderated dialogue about reliability of measurements of biobehavioral and psychosocial constructs in nursing research. Papers were contributed by four invited groups of authors composed variously of psychometricians, nursing scientists, and statisticians. The process was “open,” with authorship