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

Abstract

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