Evaluating the psychometric properties of the Grit scale in Marine recruits using Rasch analysis

Introduction Successful completion of initial military training has been suggested to be predicted by physical abilities, cognitive abilities and non-cognitive abilities such as hardiness and grit. This study aimed to assess the psychometric properties of a Dutch version of a grit measurement scale: the NL-Grit scale. Methods We assessed the factor structure, unidimensionality of the subscales, discriminative quality of the rating scale and investigated to what extend the items together can reliably measure the entire range of grit levels in Dutch Marine recruits. We used data of Marine recruit training platoons of the Royal Netherlands Marine Corps. Results Principal component analysis reflected two subscales: 'consistency of interests' and 'perseverance of effort'. Rasch analysis confirmed the unidimensionality of the intended subscales. Rasch rating scale analysis indicated that the five-point response scale was not used as intended by respondents. Disordered rating scale categories were collapsed to obtain ordered rating categories. The item and person parameters (grit levels) largely overlapped, indicating that the item spread was sufficient for measuring the entire range of grit trait levels. However, larger gaps between item location parameters suggested a low discriminative capacity of the NL-Grit scale for respondents with trait levels within the gaps. Conclusion Our evaluation of the NL-Grit scale suggests sound psychometric quality of the NL-Grit in Dutch Marine recruits. Reliability could be improved by adding items to fill the observed gaps in item content.