Does the Brief-BESTest Meet Classical Test Theory and Rasch Analysis Requirements for Balance Assessment in People With Neurological Disorders?

Elisabetta Bravini; Antonio Nardone; Marco Godi; Simone Guglielmetti; Franco Franchignoni; Andrea Giordano

doi:10.2522/ptj.20150550

Figures

Figure 2.

Person ability and item difficulty map of the Brief-BESTest. A vertical line represents the measure of the variable, in linear logits. The leftmost column locates each person's ability, from higher (top) to lower (bottom) ability. The rightmost column locates the relative difficulty of each item for this sample. A higher item measure (item 3a) reflects more difficulty in that item (higher score). By convention, the average difficulty of items in the test is set at 0 logits (indicated by M′), and participants with average ability are located at M. Horizontal dashed arrows indicate the 2 extreme threshold boundaries, and S and T represent, respectively, 1 and 2 standard deviations. Each point indicates one participant, and each hash mark indicates 2 participants. CSL-L=compensatory stepping lateral, left; CSL-R=compensatory stepping lateral, right; FRF=functional reach forward; H/T LS=hip/trunk lateral strength; SECF=stance with eyes closed, on foam surface; SL-L=one-leg stance, left; SL-R=one-leg stance, right; TUG=Timed “Up & Go” Test.

Figure 3.

Standard error of measurement (SE, expressed in logits) for the Rasch model person ability estimates and cumulative percentage of participants at each level of ability. About 30% of the sample had an SE of greater than 0.6 logit (from −4.42 to −2.08 logits and from 1.78 to 4.76 logits).

Figure 1.

Category probability curves. The y-axis represents the probability (0–1) of responding to 1 of the 4 rating categories, and the x-axis represents the corresponding performance values, calculated as person ability minus item difficulty and expressed in logits. The 3 thresholds (vertical dashed lines)—that is, the ability levels at which the response to either of 2 adjacent categories was equally likely—were at −0.91, −0.44, and 1.35 logits.