Data analyses
Data were analyzed in SPSS 27. Data set can be obtained from the last author upon request. We tested if the current intervention group (receiving a third MC) and control group differed on sociodemographic characteristics at the original baseline (Week −244) using Pearson's Characteristics of participants (Abbreviation: MC, marriage checkup.Calculated on individual rather than couple level.To evaluate the treatment effects of the third MC, we used a dyadic score model following recommendations by Iida et al. (We were able to obtain data on 95.5% of the maximum possible number of observations across Week 0−28 (844 obtained observations out of 884 possible observationsAs the MC was developed for couples across the spectrum of relationship satisfaction, we conducted sensitivity analyses for the influence of severely distressed couples on treatment effects, where we identified couples as outliers if they showed one or more “probable outlying” low score (