Speech listening study. Refer to the American Journal of Speech-Language Pathology (Feb. 1995) study, presented in Exercise 2.41 (p. 49). Recall that three groups of college students listened to an audiotape of a woman with imperfect speech. The groups were called control, treatment, and familiarity. At the end of the session, each student transcribed the spoken words.
a. Construct box plots for the percentage of words correctly transcribed (i.e., the accuracy rate) for each group.
b. How do the median accuracy rates compare for the three groups?
c. How do the variabilities of the accuracy rates compare for the three groups?
d. The standard deviations of the accuracy rates are 3.56 for the control group, 5.45 for the treatment group, and 4.46 for the familiarity group. Do the standard deviations agree with the interquartile ranges (part c) with regard to the comparison of the variabilities of the accuracy rates?
e. Is there evidence of outliers in any of the three distributions?
Exercise 2.41
Speech listening study. The role that listener knowledge plays in the perception of imperfectly articulated speech was investigated in the American Journal of Speech—Language Pathology (Feb. 1995). Thirty female college students, randomly divided into three groups of 10, participated as listeners in the study. All subjects were required to listen to a 48-sentence audiotape of a Korean woman with cerebral palsy, and all were asked to transcribe her entire speech. For the first group of students (the control group), the speaker used her normal manner of speaking. For the second group (the treatment group), the speaker employed a learned breathing pattern (called breath-group strategy) to improve speech efficiency. The subjects in the third group (the familiarity group) also listened to the tape with the breath-group strategy, but only after they had practiced listening twice to another tape in which they were told exactly what the speaker was saying. At the end of the listening-transcribing session, two quantitative variables were measured for each listener: (1) the total number of words transcribed (called the rate of response) and (2) the percentage of words correctly transcribed (called the accuracy score).The data for all 30 subjects are provided in the accompanying table.
a. Use a graphical method to describe the differences in the distributions of response rates among the three groups.
b. Use a graphical method to describe the distribution of accuracy scores for the three listener groups.
LISTEN
Control Group | Treatment Group | Familiarization Group | |||
Rate of Response | Percent Correct | Rate of Response | Percent Correct | Rate of Response | Percent Correct |
250 | 23.6 | 254 | 26.0 | 193 | 36.0 |
230 | 26.0 | 178 | 32.6 | 223 | 41.0 |
197 | 26.0 | 139 | 32.6 | 232 | 43.0 |
238 | 26.7 | 249 | 33.0 | 214 | 44.0 |
174 | 29.2 | 236 | 34.4 | 269 | 44.0 |
263 | 29.5 | 231 | 36.5 | 256 | 46.0 |
275 | 31.3 | 161 | 38.5 | 224 | 46.0 |
193 | 32.9 | 255 | 40.0 | 225 | 48.0 |
204 | 35.4 | 275 | 41.7 | 288 | 49.0 |
168 | 29.2 | 181 | 44.8 | 244 | 52.0 |
Source: Tjaden, K., and Liss, J. M. “The influence of familiarity on judgments of treated speech.” American Journal of Speech—Language Pathology, Vol. 4, No. 1. Feb. 1995, p. 43 (Table 1).
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