Psychometric validation and item invariance of the French version of the Brief Resilience Scale in a sample of French university students following the first COVID-19 lockdown

This study aimed to confirm the psychometric validity of the French version of the Brief Resilience Scale (BRS-F), as well as to evaluate its psychometric properties for the first time using item response theory, more precisely the partial credit model (PCM). It also aimed to evaluate item invariance by exploring possible differential item functioning (DIF). The 3708 participants were recruited during a cross-sectional observational study among university students in the French region of Lorraine. The results of the classical test theory method demonstrated an overall good fit of the scale to the data, with SB-χ2 = 80.84, df = 9, χ²/df = 9.0, p < 0.001, and root mean square error of approximation (RMSEA) (90% CI) = 0.046 [0.039; 0.058], standardized root mean square residual (SRMR) = 0.018, and comparative fit index (CFI) = 0.991), and good internal consistency (Cronbach's α = 0.86). The PCM also yielded a good fit, with a good internal consistency (PSR = 0.88) and overall good infit indices. A slight irregularity in response distribution was observed with the "Neutral" category, but was not a threat to the structural integrity of the scale. No statistically significant DIF was observed when tested for gender (male vs. female) or academic level (undergraduate vs. graduate). Overall, the BRS-F was a good fit for the population of university students in France in a cross-sectional design.