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Applied Inferential Statistics                     LAALCM 2021-2022                                       Joan C. Mora

Statistical Analysis Task

The SPSS data sets you need to use for this final task on statistics in this course are called “ASA”, i.e. Auditory Selective Attention (a perception task), and DNWR_SDS, i.e. Spectral Distance Score in a Delayed Nonword Repetition Task (a production task). This is a real data set from a study investigating the role of auditory selective attention in L2 learners’ ability to learn the English phonological vowel contrasts in cap-cup /kæp/-/kʌp/and feet-fit /fiːt/-/fɪt/. The DNWR test was administered twice, before and after a period of perceptual and productive phonetic training on the target contrasts /æ/-/ʌ/ (Low vowel contrast) and /iː/-/ɪ/ (High vowel contrast) using nonwords. The ASA data set is by subjects, the DNWR_SDS data set is by items. Some of the research questions below refer to the ASA data set only, others refer to both the ASA and the DNWR_SDS data sets. See below for a description of the ASA and the DNWR_SDS tasks.

ASA

Participants were presented with 64 pairs of sentences in English binaurally over headphones, each pair consisting of a target and a competing sentence. The two sentences in a pair were always different, spoken by a male and a female voice, and presented simultaneously (e.g. male: Ready CHARLIE go to BLUE SIX now; female: Ready TIGER go to RED EIGHT now). The sentences were all normalized for duration to 1700ms. A call signal (e.g. TIGER) appearing on the screen, previous to the auditory presentation of the sentences, cued the voice participants had to attend to for correctly identifying 1 of 4 colours and 1 of 8 digits visually presented on the screen. Individual ASA scores were computed by adding up all correctly identified colours and digits in each one of the two tasks up to a maximum score of 128.

Ready CHARLIE go to BLUE SIX now

DNWR_SDS

Participants performed a delayed nonword repetition task that elicited minimal pair nonwords and words targeting the two English vowel contrasts cap-cup /kæp/-/kʌp/and feet-fit /fiːt/-/fɪt/ before (T1) and after (T2) training. For each contrast participants were presented with 32 trials, 16 per vowel, 8 nonwords (on which participants had been trained) and 8 words (on which participants had not been trained) in order to assess generalization of training gains to words. Acoustic measures of the quality of the vowels were obtained and normalized and a spectral distance score (SDS) was computed to calculate the Euclidean distance between the two contrasting vowels within each one of the vowel pairs. The bigger the SDS, the larger the contrast was in the production of the contrasting vowels within each pair. A positive effect of training would therefore result in larger SDSs at post-test than at pre-test.

DNWR task procedure (listen + wait for beep + repeat)

Experimental items in the DNWR task

Task Instructions:

Based on the description of the study and the tasks above, your task is to answer the research questions below. You need to answer these questions by conducting any necessary data analyses and statistical tests using the ASA and DNWR_SDS data sets provided, or creating new data sets if necessary. You need to explain the tests you do accurately and report the results that support the answers to the questions appropriately.

You need to upload two documents only in Moodle:

1- Surname_Name_RQs&Answers.doc

This document should include:

– The research questions.

– Your answers to the research questions with the report of the results of your analyses              (descriptives) and the outcome of the statistical tests you have conducted, both      reported as they would be reported in a scientific article.

2- Surname_Name_SPSS

– This is the SPSS output (in PDF format) containing all of the outputs of the main relevant analyses you have conducted.

Answer the following questions*:

1. Was the phonetic training period effective at increasing participants’ SDSs between the contrasting vowels?

2. Was the phonetic training period equally effective for both the Low and the High vowel contrast?

3. Was the phonetic training period equally effective for trained and untrained words? i.e., did training gains result in generalization gains showing learning having taken place?

4. What is the amount of variance ASA scores explain in L2 learners’ ability to distinguish between contrastive vowels in production?

5. To what extent are individual differences in auditory selective attention (ASA) related to the size of training gains in spectral distance scores in /æ/-/ʌ/ and /iː/-/ɪ/?

*the answer to the questions must be based on your data reports for both descriptive statistics and the outcome of statistical tests.