The results indicated that at most levels of the background characteristics studied, there were statistically significant differences in the means of the four underlying latent factors (reading, listening, speaking, and writing) representing English-language proficiency (ELP). Overall, the effect size differences on the reading, listening, speaking, and writing latent factors among the levels for each of the background variables studied ranged from small to medium. The results of this study provide empirical evidence of the association and possible influence of test-taker background characteristics on the four underlying latent factors representing ELP and, thus, on test performance.