Statistical bias in the assessment of binaural benefit relative to the better ear

Abstract

The comparison of measured binaural performance with the better of two monaural measures (one from each ear) may lead to underestimated binaural benefit due to statistical sampling bias that favors the monaural condition. The mathematical basis of such bias is reviewed and applied to speech reception thresholds measured in 32 bilateral cochlear implant (CI) users for coincident and spatially separated speech and noise. It is shown that the bias increases with test-retest variation and is maximal for uncorrelated samples of identical underlying performance in each ear. When measured differences between ears were assumed to reflect actual underlying performance differences, the bias averaged across the CI users was about 0.2 dB for coincident target and noise, and 0.1 dB for spatially separated conditions. An upper-bound estimate of the bias, based on the assumption that both ears have the same underlying performance and observed differences were due to test-retest variation, was about 0.7 dB regardless of noise location. To the extent that the test-retest variation in these data is comparable to other studies, the results indicate that binaural benefits in bilateral cochlear implant users are not substantially underestimated (on for average) when binaural performance is compared with the better ear in each listening configuration.

Speech-in-noise screening tests by internet, Part 3: Test sensitivity for uncontrolled parameters in domestic usage

“…agree with differences of 0.6 -0.7 dB reported in literature (Plomp & Mimpen, 1979b, McArdle et al, 2012. Also, it is known that speech discrimination under diotic conditions is superior to monotic listening (Kaplan & Pickett, 1981;Davis et al, 1990;van Hoesel & Litovsky, 2011;McArdle et al, 2012). The diotic benefi t in this study is 0.9 dB in the lab and 1.6 dB at home (see Table 4).…”

Having Two Ears Facilitates the Perceptual Separation of Concurrent Talkers for Bilateral and Single-Sided Deaf Cochlear Implantees

“…In one analysis, the better ear was defined for each listener as the ear that yielded the best mean percentage-correct performance across all monaural conditions. However, van Hoesel and Litovksy (2011) argued that using the outcome measure as the means of identifying the better ear can lead to a bias toward observing an effect of ear of presentation when one is not present. Therefore, a second analysis was conducted that defined the better ear based on patient self-report.…”

Spatial release from masking in children with bilateral cochlear implants and with normal hearing: Effect of target-interferer similarity

“…A lack of differences in SRTs in BiCI groups suggests that as children gain more experience with their CIs, the ability to segregate the target source at a lower level relative to the interferer does not significantly improve. Therefore, it is most likely the limitations of the CI device, rather than experience, which limit access of BiCI users to cues that aid in identification of the target source in noisy environments (van Hoesel and Litovsky, 2011).…”

“…The overall difference in SRM between NH and BiCI groups suggests that cues necessary for spatial hearing are not delivered by current CI processor technology . Additionally, the independent functionality of the current processors likely cause binaural cues to be either absent or inconsistent in BiCI users (van Hoesel and Litovsky, 2011).…”