"Will you complete this survey too?" Differences between individual versus dyadic samples in relationship research.

This study examines the ways in which collecting data from individuals versus couples affects the characteristics of the resulting sample in basic research studies of romantic relationships. From a nationally representative sample of 1,294 individuals in a serious romantic relationship, approximately half of whom were randomly selected to invite their partner to participate in the study, we compare relationship, individual, and demographic characteristics among 3 groups: individuals randomized to invite their partner and whose partner participated in the study, individuals randomized to invite their partner but whose partner did not participate, and individuals who were not randomized to invite their partner. Results indicated that individuals whose partner participated reported the highest levels of relationship and individual well-being relative to comparison groups, as well as individuals who participated alone despite being asked to invite their partner, reported the lowest levels of relationship and individual well-being relative to comparison groups. Effect size magnitudes indicated the strongest group differences with respect to relationship variables, particularly cognitive appraisals of overall relationship stability and satisfaction. Implications for romantic relationship research and study design are discussed. (PsycINFO Database Record (c) 2020 APA, all rights reserved).