Short Grit Scale (Grit-S): New evidence based on CFA and MIRT models

Abstract

Studying grit's measurement helps to understand this psychological phenomenon associated with success. Grit-S structures of one-factor and two-factor have been reported in the literature, but there is a lack of reports based on Item Response Theory (IRT). Therefore, two objectives were proposed: to determine the factorial structure of the Spanish version of the Grit-S and explore the instrument through a Multidimentional Item Response Theory (MIRT) analysis. A nonprobabilistic sample of 899 subjects (41.0% female) was evaluated. The 8 items grit scale was used. The Confirmatory Factor Analysis (CFA) showed that the two-factor model obtained a good fit (CFI = 0.97, TLI = 0.95, RMSEA [90%CI] = 0.08 [0.07, 0.10]) unlike the one-dimensional model. An exploratory comparison analysis by MIRT also revealed that the two-factor model performed better (p < 0.001). Consequently, a confirmatory analysis determined an adequate fit of the two-factor model (C2 = 45.4; RMSEA [90%CI] = 0.05 [0.04 - 0.07]; TLI = 0.97; CFI = 0.99). Multidimensional discrimination values were within the expected range (> 1; > 1.5), although item 2 had low discrimination. Regarding difficulty, all items had a monotonic increase. The two-factor model fits the data by both CFA and MIRT. Both complementary analyzes demonstrate the potential of Grit-S to measure latent consistency and perseverance factors.