Fig. 2
From: Assessment of the Chinese Resident Health Literacy Scale in a population-based sample in South China
Test information and participant ability. Ability signifies health literacy estimated using the maximum-likelihood method. Ability in the item response theory (IRT) model practically (though not exclusively) ranged from −3 to +3. The test information reached a peak when the ability was between −1 and 0; this indicates that the measurement exhibited highest discriminative power among participants with limited and under-average ability with respect to health literacy