2.3 Analysis of variance (ANOVA) and Scheirer-Ray-Hare
Grubb’s tests and normality tests (Shapiro-Wilk) were performed in
Origin to identify and discard outliers (OriginPro, Version 2018G,
OriginLab 275 Corporation, Northhampton, MA, USA). Two factorial
variance analyses with measuring repetitions were performed to evaluate
the influence of Fe2+ and flow velocity on biofilm
development and structure. In case of non-normality, a Scheirer-Ray-Hare
test was applied. Three hypotheses were picked with the following
predications:
H1: No differences in structure due to usage of
different flow velocities \(u\)
H2: No differences in structure due to usage of
different iron concentrations \(c\)
H3: No correlation between both parameters \(u\) and\(c\)
To determine the approval or rejection of the hypotheses, calculated\(p\)-values were compared to a significance level of \(\alpha\)< 0.01, whereby values p < \(\alpha\)describe the rejection of the individual hypothesis. Variance analyses
were performed in Excel (Excel version 15.11, Microsoft Corporation,
Washington, USA).