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. 2015 Jul 11;15:637. doi: 10.1186/s12889-015-1958-0

Fig. 2.

Fig. 2

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