Evaluating relative speech recognition performance using the proficiency factor and rationalized arcsine differences

This study evaluated two measures that have been used to compare the performance of particular subjects to outcomes predicted by the articulation index (Al). One measure was the proficiency factor, that is, the ratio between the Al derived from a test score and the Al derived from objective measurements of speech and noise spectra. The other measure was the difference between rationalized arcsine transforms of the observed score and the score predicted from the Al. The results indicated that rationalized arcsine differences are statistically superior to proficiency factors for comparing two sets of scores. Proficiency factors are best used to correct the Al, and thus an expected score, for the effects of subject variables that might bias the comparison. An assessment procedure that combines the strengths of both measures is described.