This article concerns how to estimate reliability (defined as the internal consistency of
responses to a scale) in designs that are commonly used in studies of within-person
variability. I present relevant issues, describe common errors, make recommendations for
best practice, and discuss unresolved issues and future directions. I describe how to
estimate the reliability of scales administered in studies in which observations are nested
within persons, such as daily diary and “beeper” studies and studies of social interaction�…