CHAPTER ONE: OVERVIEW AND RATIONALE FOR THE STUDY
4.6 PHASE 2: APPLICATION OF THE DEVELOPED ZULU SRT WORD LIST
4.6.1 Aim three: To assess the application of the Zulu SRT word list on a clinical normative population of KZN
4.6.1.1 Participants
Twenty-six Zulu First Language Speakers were considered for this phase of the study. The participants were University students who spoke Zulu as a First language, but were practically and functionally proficient in English. This was determined as all the students included had passed matric level of English.
4. 6.1.2 Sampling method
Purposive sampling was used. The motivation for the use of purposive sampling was similar to objective one in aim two of the study. Participants were recruited via advertisements as described in aim two of the study above.
4.6.1.3 Sample selection criteria
The selection criterion was as per objective one of Aim two of the study. The researcher also ensured that all participants were First language Zulu speakers of the Durban, Pietermarizburg region and were proficient in English.
4.6.1.4 Data collection process
All participants were screened for normal hearing bilaterally as per discussion in objective one of aim two of the study. This included a case history, immittance testing, pure tone testing. The details on the procedure followed are indicated in Appendix I.
4.6.1.5 Procedure for SRT testing using the Zulu words
Bilateral SRT were established on twenty six participants. There were established in all participants who presented with normal hearing based on the case history, immittance battery and pure tone testing. The procedure for eliciting the SRT is described below.
• Instructions to the participants: A Zulu First language speaker instructed each participant. ASHA (1988) stipulated that instructions for SRT must be done in the language of the client.
• Familiarization to test material: ASHA (1988) stated that this process is an essential step in the SRT procedure and should not be eliminated. The participants were familiarized with the test items by presenting the list in written format to the client as well as the recorded list was played to them at comfortable hearing levels (30dBHL). The participants were expected to repeat each of the words. This step was necessary to ensure that the participants knew the exact words in the test list and the participants could make adequate responses to each word on the list. Any of the words that the participants had difficulty understanding or repeating were eliminated from the list.
• Method for eliciting SRT: For the purposes of this study, the recorded presentation of the word list were used i.e. the words were recorded on a CD, which were routed through the GSI 61 audiometer. The motivation for the use of recorded materials has been made in earlier sections. The Chaiklin and Ventry (1964) descending method for eliciting SRT was used i.e. 5dB descents. It was found that this method produced similar findings as the ascending method. Further, Hirsh et al. (1952) found that the descending method almost exclusively was used during the development of speech materials and is widely used at present clinically. Two Zulu First Language speakers and the researcher scored the responses from the participants on a form developed by the researcher (see Appendix M).
• Response mode: The mode of response used was verbal repetitions.
• Recording of results: The speech threshold was recorded in dBHL. The test responses were verified between two Zulu First language speakers and the researcher before being recorded.
• Criteria used to determine SRT: The SRT was defined as the lowest level in dB HL, at which the subject was able to correctly identify 50% of the words presented (ASHA, 1988).
The three-frequency audiogram procedure was used to calculate the pure tone average in hearing threshold level (PTA HL). According to Carhart (1965) the simple averaging of the octave frequency 500Hz, 1000Hz and 2000Hz is adequate for estimating the sensitivity for speech. Thus, researchers have advocated the need to compare the PTA with the SRT. Each participant's PTA was correlated with his or her SRT values. Thereafter for the purposes of comparison, the participants were presented with the CID W-2 list via a CD recording. This word list was recoded on track two of the CD (Appendix S).
4.6.1.6 SRT using recorded English word list
The English CIDW-2 list was recorded on the CD by the same speaker who spoke English as a second language. The speaker was considered functionally and practically proficient in English. The second language English speaker was used for the recording, in order to control for any dialectal influences if a first language English speaker presented the words to the participants. An SRT was established using the recorded version of the word list. This was established on all 26 participants bilaterally. The motivation for establishing the SRT in English was to serve as comparison between PTA/SRT (Zulu) and PTA/SRT (English). The procedure followed was similar to that recommended by ASHA (1988). The familiarization process was the same as discussed above. An SRT value was recorded and the SRT values were used as part of the overall analysis.
4.6.1.7 Analysis of data
All data were analysed using the computerized SPSS version 11.6 method. In order for the researcher to establish the correlation between PTA and SRT (Zulu) values, the Parametric Pearson Product moment correlation co-efficient statistic was used as a quantitative procedure. This correlation is a parametric index, which serves a variety of functions, one of which is to determine the validity of measurement techniques and materials (Hinkle, 1982). In the present investigation the SRT values (Zulu) were correlated with the Pure Tone Averages for each of the participants, as it is widely accepted that these two measures serve as validity checks of each other (Konkle & Rintlemen, 1983). The pure tone values for the twenty-six participants across both the left and right ears were carefully examined and it was indicated that were no significant ear differences. This implied that there was no more than a 5dB difference between the ears for the pure tone average values. This allowed the researcher to group the data for left and right ears and thus increases the N value to 52. The critical values of the normal distribution were applied when interpreting data and testing for significance were done at the alpha level of p
= 0 , 0 1 .
In addition, the researcher used a descriptive analysis approach to evaluate the difference in SRT score for the Zulu versus SRT in English in relation to the PTA, using percentage counts.