Table 1.
Item, subscale, and overall scores for the DBAS-16.
Table 2.
Four-factor confirmatory factor analysis of the DBAS-16.
Table 3.
Summary of item parameters estimates.
Table 4.
Summary of item information estimates.
Fig 1.
Item characteristic curves for dysfunctional Beliefs and Attitudes about Sleep (DBAS-16) scale items 6, 8, 11 and 15.
The left y-axis represents the probability of choosing a response category and the right y-axis represent the degree of information provided across the underlying trait continuum. The peak of each response function represents the maximum probability of choosing that response category given a theta level (i.e., underlying trait). Item information function is indicated with a dashed line. IRTPRO (Version 4.2) by default shows response alternatives (strongly disagree [1] to strongly agree [10]) as 0 to 9.
Fig 2.
Test information function of the expectations, worry/helplessness, consequences, and medication subscales.
The peak of the total information curve represents the theta level (i.e., degree of unhelpful beliefs and attitudes about sleep) at which the Dysfunctional Beliefs and Attitudes about Sleep (DBAS-16) Scale most accurately predicts degree of dysfunctional beliefs and attitudes about sleep (i.e., worry, expectations, attributions, consequences). The peak of the standard error curve represents the theta level at which the DBAS-16 has the most error in predicting the degree of dysfunctional beliefs and attitudes about sleep.