*3.5. Statistical Analyses*

The influences of the macroalgal species, extraction technology and extraction time post-treatment on the extracted phytochemicals (TPC, TPhC, TFC, TSC and TTC) and antioxidant activities (DPPH and FRAP) were analysed by multivariate general linear model in SPSS version 24.0. The differences were further analysed by either Tukey's HSD post hoc tests or Student's *t*-test. Differences were considered to be significant at *p*-values < 0.05. The relationships between the composition of the extracts and their

antioxidant properties were explored in R version 4.0.2 [55]. The statistical packages "ggplot2" and "corrplot" were used to generate the correlation matrix [56] and "cor.mtest" produced the *p*-values for the Pearson's correlation matrix. The variance in the data set was further analysed by principal component analysis (PCA) using Equamax rotation with Kaiser normalisation extracting the weight for each component with eigenvalues higher than 1 using SPSS version 24.0.
