Table 4.
Mean values (with standard deviation in parentheses) and effect sizes (Cohen’s d) for each dependent variable during both speaking conditions.
| Dependent Variable | Control group | Persons who stutter | ||||
|---|---|---|---|---|---|---|
| Effect size | Experimental mean | Control mean | Effect size | Experimental mean | Control mean | |
| Peak pressure (cm H2O) | −.59 | 6.95 (1.23) | 7.88 (1.86) | .22 | 7.13 (2.09) | 6.66 (2.22) |
| Pressure rise time (ms) | −.31 | 83.50 (20.35) | 89.91 (21.50) | .31 | 96.23 (28.16) | 89.03 (15.94) |
| Maximum air flow(cc/s) | −.43 | 551.22 (193.65) | 662.71 (312.13) | −.17 | 551.73 (232.73) | 597.95 (314.33) |
| Vowel midpoint air flow (cc/s) | −.24 | 149.29 (60.57) | 165.63 (75.25) | −.06 | 148.91 (70.14) | 153.51 (75.12) |
| Vowel duration (ms) | .99* | 132.15 (24.81) | 113.67 (8.86) | .72* | 154.61 (34.09) | 130.99 (31.39) |
| Voice onset time (ms) | .10 | 55.66 (10.67) | 54.72 (8.85) | .30 | 58.22 (15.61) | 53.61 (15.56) |
| Fundamental frequency (Hz) | .07 | 149.78 (38.78) | 147.20 (30.97) | .11 | 132.66 (35.09) | 128.59 (35.41) |
| Phonated intervals | ||||||
| Overall mean (ms) | .80** | 303.98 (74.15) | 256.51 (39.31) | .40 | 330.43 (74.02) | 296.63 (92.07) |
| 30–100–ms bin | −.69* | 12.04 (8.38) | 16.80 (5.13) | −.80* | 9.35 (5.09) | 17.38 (13.27) |
| 101–150–ms bin | −.41 | 14.49 (6.92) | 16.63 (2.49) | −.60 | 12.66 (6.14) | 15.81 (4.24) |
| 151–200–ms bin | −.21 | 13.07 (2.14) | 13.59 (2.86) | .01 | 15.20 (4.78) | 15.17 (3.06) |
*
p < .05.
**
p = .01