Using Rasch Analysis to Assess and Improve the Measurement Properties of a Questionnaire With Few Items: The York Binaural Hearing-Related Quality of Life (YBHRQL) Questionnaire.

OBJECTIVES

The York Binaural Hearing-Related Quality of Life questionnaire is a condition-specific preference-based instrument sensitive to advantages of binaural over monaural hearing. Respondents use 5-point scales to report the difficulty experienced with three dimensions of listening that are easier or more successful when hearing is binaural: understanding speech in spatially separated noise, localizing sources of sound in azimuth, and the associated effort and fatigue. Previously, a preference value was estimated for each combination of dimension and level so that a value of binaural utility could be assigned to a respondent to inform analyses of cost effectiveness. The present objective was to determine whether the questionnaire conforms with the Rasch model sufficiently well for estimates of the binaural abilities of respondents to be obtained on an interval scale to inform parametric analyses of clinical effectiveness.

DESIGN

Data were obtained from unilateral cochlear implantees (N = 418; 209 ≤62 years; 209 ≥63 years) and members of the public (N = 325; 207 ≤62 years; 118 ≥63 years). A subset of implantees (N = 118) responded at test and retest. Responses were fitted to the partial credit model using the Extended Rasch Modeling package. Conformity with the model was evaluated in six ways: the ordering of response categories ( Monotonicity ) was assessed with plots of response probability against ability; differential item functioning ( DIF ) was assessed by analyses of variance of standardized response residuals; alignment of participants' abilities with item difficulties ( Targeting ) was assessed with person-item maps; fit to the model ( Fit ) was assessed by comparing the means and variabilities of observed and expected responses, and by comparing observed values with analyses of simulated datasets; the hypothesis that item difficulties and participants' abilities were measured on a single underlying scale ( Unidimensionality ) was assessed with principal components analyses of standardized response residuals.

RESULTS

Values of fit statistics were toward the lower end of the acceptable range. Comparisons with analyses of simulated datasets showed that low values were primarily the result of the structural limitation of including only three items. Modal values of the probabilities of response categories were ordered monotonically, but some response thresholds were disordered because of under-use of one category. Pooling categories to correct disordered thresholds resulted in estimates of ability that were less discriminatory of differences within and between groups, and showed less reproducibility between test and retest, than did the original estimates. Neither source-related DIF nor gender-related DIF arose. Uniform age-related DIF arose for the speech-in-noise item and could be managed by resolving the item. The resulting estimates of ability and difficulty were well targeted and unidimensional.

CONCLUSIONS

The York Binaural Hearing-Related Quality of Life questionnaire, with three items each with five response categories, conforms with the Rasch model sufficiently well to yield practically useful measures of the abilities of participants. The trait measured by the questionnaire aligns with the ability to benefit from binaural hearing. More discriminatory measurement of this ability would be achieved with more items. Nonetheless, the questionnaire possesses the virtue that responses to the same three questions can be scored in different ways to inform parametric analyses of both cost-effectiveness and clinical effectiveness.