The French MBAA2 sentence recognition in noise test for cochlear implant users

Figures & data

Figure 1. Examples of reduction of fixed-SNR testing data points to obtain the SNR50: The sigmoid (red curve) was fitted using an iterative, least-squares Levenburg-Marquart (L-M) method from all four points, three intermediate and the maximum, to give the SNR50 (short red line); three analytic sigmoid estimates of the SNR50 were calculated from two intermediate points and maximum (short black lines); the linear fit gives a large error in estimating the SNR50 when using intermediate data points 1 and 3 (e.g. short gold line).

Table 1. Summary statistics for 15 CI listeners in Study 2 using the French matrix and MBAA2 sentence tests.

	Mean (dB)	Standard deviation	95% C.I. difference	Paired t-test for difference
French matrix test adaptive
SNR50 N = 15	21.6	28.4
SNR50 N = 10 (<15 dB)	4.4	4.4
Test–Retest	0.7	1.3	−1.9:3.2	t[9] = 1.57	p = 0.15
French matrix test iterative fit
SNR50 N = 10 (<15 dB)	5.6	4.9
Slope (%/dB)	6.7	2.6
French matrix test
Iterative fit–adaptive N = 10	1.1	2.1	−3.1:5.3	t[9] = 1.66	p = 0.13
MBAA2 iterative fit
SNR50 N = 14	2.9	3.5
Slope (%/dB)	10.4	5.1
MBAA2 dB (analytic fit)
SNR50 N = 14	2.9	3.6
Slope (%/dB)	11.1	4.8
MBAA2: fit–analytic N = 14	0.0	0.5	−0.9:0.9	t[13] = 0.14	p = 0.89

C.I.: confidence interval.

SNR50 values and test–retest differences are given, as well as differences in SNR50 values obtained using two different methods with the same test. All values are signal-to-noise ratios (SNR50) in dB unless slope is indicated.

Table 2. Summary statistics for 15 CI listeners in Study 3 using MBAA2.

	Mean	Standard deviation	95% C.I. difference	Paired t-test for difference
Fixed SNRs
10 dB SNR: % correct score	92.8	5.2
Test–Retest	0.9	4.4	−7.8:9.6	t[14] = 0.82	p = 0.43
5 dB SNR: % correct score	79.2	10.4
Test–Retest	−1.8	9.1	−19.7:16.1	t[14] = 0.76	p = 0.46
2 dB SNR: % correct score (N = 6)	37.8	9.0
0 dB SNR: % correct score (N = 9)	31.2	9.6
2/0 dB SNR Test–Retest	−1.3	14.9	−30.6:28.0	t[14] = 0.33	p = 0.75
Analytic SNR50
SNR dB	2.1	1.0
Test–Retest SNR dB	0.1	1.2	−2.2:2.4	t[14] = 0.41	p = 0.69
Slope (%/dB)	13.0	4.1
Test–Retest slope (%/dB)	−0.8	4.1	−8.8:7.2	t[14] = 0.73	p = 0.48

SNR: signal-to-noise ratio; C.I.: confidence interval.

Means and standard deviations are across both test and retest where not indicated as “Test–Retest.” The 95% confidence intervals for test–retest differences were derived from the standard deviation of the differences.

Figure 2. Scores for three lists exhibiting significant differences in mean scores (points) compared to all lists, and those nine having low item to total correlation (lines): Confidence intervals of scores for individual listeners are represented by the darker (68%) and lighter (95%) shading.

Table 3. Summary statistics for the full original set of 36 MBAA2 lists, and the reduced set of 24 lists.

MBAA set	N lists	List variance	Listener variance	Residual variance	ICC consistency	ICC agreement
Original	36	10.9	52.7	44.2	0.54	0.49
Reduced	24	5.3	68.8	33.6	0.67	0.64

ICC: intra-class correlation.