The alphas and omegas of validity and reliability: Contemporary advances in evaluating and selecting instruments for quantitative research with emerging adults.

The current chapter presents a non-technical description of the most important features of the current conceptualization of validity and reliability and the best practices to evaluate them. The chapter is organized into two sections. The first section introduces the contemporary view of validity, which stresses that validity is unified (the core of validity is construct validity, which can be argued for by collecting different kinds of evidence) and contextualized (validity always depends on the population, place, and time in which the test is applied). Implications in terms of validation practices are presented. The second section explains why the widely used coefficient alpha may be an inadequate index of reliability and suggests substituting it with coefficient omega. Guidelines in both sections of the chapter are demonstrated using the procedures adopted to develop and validate the Multidimensional Subjective Financial Well-being Scale in a sample of Italian emerging adults.