Rasch Analysis of Word Identification and Magnitude Estimation Scaling Responses in Measuring Naïve Listeners' Judgments of Speech Intelligibility of Children With Severe-to-Profound Hearing Impairments

Abstract

Purpose Speech intelligibility research typically relies on traditional evidence of reliability and validity. This investigation used Rasch analysis to enhance understanding of the functioning and meaning of scores obtained with 2 commonly used procedures: word identification (WI) and magnitude estimation scaling (MES). Method Narrative samples of children with hearing impairments were used to collect data from listeners with no previous experience listening to or judging intelligibility of speech. WI data were analyzed with the Rasch rating scale model. MES data were examined with Rasch partial credit model when individual scales were unknown, and the Rasch rating scale model was used with reported individual scales. Results Results indicated that both procedures have high reliability and similar discriminatory power. However, reliability and separation were lower for MES when scales were unknown. Both procedures yielded similar speech sample ordering by their difficulty. However, sampling gaps were noted as well as item misfit issues. Conclusions Functioning wise, both WI and MES procedures were highly reliable in measuring speech intelligibility, and measurement precision may be increased by asking participants to report their individual scales when using MES. Meaning wise, operationalization of speech intelligibility did not change when either WI or MES procedure was used. However, the sample selection procedure needs to be further refined to allow for a wider selection of stimuli.