Bias in assessing binaural advantage

Attention is drawn to a bias which may occur in assessing binaural advantage in research studies and in individual clinical cases. It applies to any procedure in which binaural advantage is defined as the difference between binaural performance and the performance of whichever ear performs better. Binaural performance should be compared with the performance of the better ear but in some instances this does not happen because test variability will result in a higher score being obtained with the poorer ear. When these higher scores from the poorer ear are substituted for the lower scores of the better ear the mean 'better' ear score is inflated and binaural advantage is underestimated. A method is presented for calculating the degree of bias, and procedures for minimizing bias are discussed.