Date Published: February 28, 2019
Publisher: Public Library of Science
Author(s): Tanja Zimmermann, Martina de Zwaan, Nina Heinrichs, Wen-Jun Tu.
The Quality of Marriage Index (QMI) is a 6-item internationally widely-used instrument assessing relationship satisfaction. This study aimed to evaluate (1) the psychometric properties of the German version in a representative sample of the German general population (N = 1431) as well as (2) effects of gender and age on relationship satisfaction. All participants were in a relationship. The German QMI demonstrates good item characteristics and excellent reliability (α = .94). The proposed one-factor solution was replicated. Differences in scoring on the QMI showed that males scored higher than females and differences between younger and older participants were found. The findings suggest that the German version of the QMI is suitable to reliably measure relationship satisfaction and may therefore be used as a brief screening instrument in a variety of settings and research questions. A cross validation in a sample of couples seeking help for relationship difficulties should be considered in future research. The limited number of items and the one-factor-solution do not suggest this instrument as a fine-tuned assessment tool for different dimensions of relationship satisfaction.
Relationship quality has been demonstrated to be an important indicator of adult, couple, and child well-being. Being in a happy marriage is related to better psychological and physical health. This effect depends mainly on the relationship quality and not on partnership status in isolation [1,2]. In contrast, divorce and relationship deterioration are omnipresent and provoke substantial mental and physical health costs on individuals and society . Low relationship quality emerged as a significant risk factor for mental health symptoms . For example, there is a high association between relationship distress and depression as well as substance abuse . Moreover, relationship distress has been associated with higher incidence of both mental disorders  and poorer physical health . The impact of relationship satisfaction is also reflected in a higher use of medical services of spouses in low quality relationships and diminished medical treatment adherence [8,9]. In addition, relationship quality is considered as an important impact factor on quality of life, e.g. for couples with chronic diseases such as cancer in the U.S. and Germany [10–12]. Thus, there is substantial need for (early) detection of deteriorating relationships before serious and irreversible damage has occurred.
The purpose of the present study was to examine the psychometric properties of the German version of the QMI in a representative sample as well as effects of gender and age on relationship satisfaction. The QMI which was developed by Norton , is an internationally extensively used instrument assessing relationship quality. The six-item German version showed high internal consistency. The construct validity of the German version of the QMI was examined using PAF and CFA. Results from the EFA indicated a one-factor solution which replicated the original factor structure and explained 81.3% of the variance. The one-factor model showed a good to excellent fit in a CFA confirming the one-factor structure of the original version and supporting preliminary results from a first examination of the German version . These results suggest that the QMI is a very homogenous measure that may be used if one is interested in a global, uni-dimensional evaluation of relationship satisfaction.