Mediation and ANCOVA Models to Study the Influence of Solvent Retting Traits and Plant Physique on Bast Fiber Yield and Retting Time

Abstract

ABSTRACT The study aims in applying two statistical tools to analyze the retting behavior of plant stems for extracting bast fibers for industrial applications. At first, a mediation model is employed to investigate the first hypothesis of this work that involves studying the color response of the retted solvent as a function of retting time on the responsible variable, fiber yield (%). Statistically, there is a significant indirect effect of retting time on fiber yield (%) through retting trait (β = −0.0142, 95% C.I. [−0.0274, −0.0011]) – a statistical inference bolstered by the Sobel test result, confirming the mediation effect (p-value = 0.0329 < 0.05; z-score = −2.1334; bootstrapping of 5000 resamples). Next, the second hypothesis of the current work involves analyzing the impact of stem form-factors on their retting time using the statistical tool, ANCOVA. The partial- η2 indicates that cultivar treatment accounts for 30% variance of the retting time while controlling for the effects of two covariates – diameter and length of the stems, in this case. By controlling the Type-I error, Bonferroni and similar post-hoc tests also confirm the statistical significance of cultivar categories pertaining to their mean retting time. Future work could focus on these underlying hypotheses and study the impact of microorganisms, environmental factors, and cultivar treatment variables on the retting time to optimize the overall fiber yield and production process.