Table 6.

Comparisons between listeners with CI's empirical speech intelligibly scores and speech intelligibility index (SII) predictions incorporating different demographic and perceptual–cognitive predictors.

Model	RMSE
1. SII	0.341
2. SIIHLD	0.167
CI-corrected a
3. ${\mathrm{SII}}_{\mathrm{CI}}=\mathrm{SII}\frac{\left(6.16\mathrm{DST}\right)}{100}$	0.117
4. $=\mathrm{SII}\frac{\left(6.16\mathrm{DST}-0.60\mathrm{GDT}\right)}{100}$	0.137
5. $=\mathrm{SII}\frac{\left(6.16\mathrm{DST}-0.60\mathrm{GDT}-0.44\text{deaf}\right)}{100}$	0.166
6. $=\mathrm{SII}\frac{\left(6.16\mathrm{DST}-0.60\mathrm{GDT}-0.44\text{deaf}+\mathrm{AA}\right)}{100}$	0.058 b

Note. RMSE = root-mean-square error; SII = speech intelligibility index (normal hearing); SII_HD = SII corrected for hearing loss desensitization; CI = cochlear implant; SII_CI = CI-corrected SII; DST = auditory digit span score; GDT = gap detection threshold (ms); deaf = duration of deafness (years); AA = aided audibility (dB HL).

^a Scaling factors for GDT, deaf, and DST were based on the coefficients determined via multiple regression analysis (see Table 5). The 100 divisor term is used to ensure predicted SII_CI scores are bounded in the range of the original SII (0–1).

^b Best fitting model based on RMSE minimization (cf. Figure 3C).