The Optimism-Pessimism Short Scale-2 (SOP2): a comprehensive validation of the English-language adaptation

Abstract

The Optimism-Pessimism Short Scale-2 (SOP2) described in this article measures the psychological disposition of optimism with two items. SOP2 is the English-language adaptation of an originally for the German language developed scale. Because an empirical validation of this English-language SOP2 was hitherto lacking, the aim of the present study was to assess the psychometric properties (objectivity, reliability, validity) of the English-language adaptation and to investigate measurement invariance across both language versions using heterogeneous quota samples from the UK and Germany. Our results show that the English-language adaptation has satisfactory reliability coefficients and is correlated with 10 external variables in the study (e.g., self-esteem, Emotional Stability, life satisfaction). Moreover, scalar measurement invariance of the scale holds when comparing the UK and Germany, implying the comparability of latent (co)variances and latent means across the two nations. As an ultra-short scale with a completion time of < 20 s, SOP2 lends itself particularly to the assessment of dispositional optimism in survey contexts in which assessment time or questionnaire space are limited. It can be applied in a variety of research disciplines, such as psychology, sociology, or economics.