Assessment of reliability
Several criteria must be met to achieve high reliability in perceptual assessments. The speech material should be collected in a standardized manner (Lohmander & Olsson, 2004; Sell, 2009), and assessments should be made from audio or audio-video recordings made with high-quality equipment (Lohmander et al., 2009). Depending on the research question, appropriate speech material should be used (e.g., word naming, sentence repetition, conversational speech) and be clearly described. In cross-linguistic studies, it is crucial to use phonetically identical speech samples, and it is essential to be aware that the linguistic background may affect the listener's perception of speech (Hutters & Henningsson, 2004). As listeners may have different internal standards (Kreiman et al., 1993), they must calibrate their listening to become coherent (Chapman et al., 2016; Sell, 2005; Sell et al., 2009). It is recommended to have at least two impartial listeners conducting assessments, as treating SLPs/SLTs may exhibit bias. Additionally, the calculation method for reliability should be disclosed. If these criteria are not met, the reliability, and thus the validity, of the speech outcome must be questioned.
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