An investigation of left–right vocal fold symmetry in rheological and histological properties

Abstract

NA. Laryngoscope, 128:E359-E364, 2018.

Paired versus two-group experimental design for rheological studies of vocal fold tissues

“…We also found that if the correlations among rheological data are ignored during statistical analysis, type I errors will be substantially inflated. Although it was previously noted that the widely used regression-fitting methods are not suitable for the statistical analysis of data generated from repeated measurements (Xu et al, 2017;Xu et al, 2018), the current study demonstrated for the first time exactly how such inappropriate statistical methods affect the outcome of vocal fold rheological data analysis.…”

“…As shown in Table 1, frequency is always one of the fixed effects in the models because G' and η' are functions of frequency. Our recent study also showed that it was preferable to treat frequency as a categorical variable (Xu et al, 2018). Another fixed effect is the treatment effect, for the assessment of possible significant relationship between tissue rheological properties and a treatment.…”

“…Additionally, intra-animal or human subject correlation exists among measurements obtained from the left and right vocal folds of the same subject. To include this hierarchical correlation structure into the vocal fold rheological data analysis, we employ the mixedeffects model approach (Xu et al, 2017;Xu et al, 2018). The mixed-effects model refers to the use of both fixed and random effects in the same analysis (Laird and Ware, 1982;West et al, 2014).…”

“…The mixed-effects model refers to the use of both fixed and random effects in the same analysis (Laird and Ware, 1982;West et al, 2014). The within-subject and within-vocal fold correlations can be accounted for by including subject and vocal fold random effects in the model (Xu et al, 2017;Xu et al, 2018). The mixed-effects models previously developed for the statistical analysis of vocal fold rheological properties are summarized in Table 1.…”

“…Viscoelastic shear properties of the rabbit vocal fold lamina propria were measured under a small strain (2% or 3%) to ensure stress-strain linearity (Xu et al, 2017;Xu et al, 2018).…”