add statistics and reproducibility assay and protocol

assays/StatisticsAndReproducibility/protocols/StatisticsAndReproducibilityProtocol.md

+## Statistics and reproducibility
+
+All experiments were performed with full factorial (biological and technical) replication. Competition experiments using SynComs were in addition repeated multiple times (Extended Data Fig. 1) using independent bacterial communities. Whenever bacterial abundances or plant growth parameters were compared, we used a two-sided, non-parametric Mann–Whitney test or, in the case of multiple comparisons, a Kruskal–Wallis test, followed by a Dunn’s post hoc. Whenever appropriate, P values were adjusted for multiple testing using the Benjamini–Hochberg method (α = 0.005). Statistical tests on beta-diversity analyses were performed using a PERMANOVA test with 5,000 random permutations. Whenever boxplots were used in figures, data were represented as median values (horizontal line), Q1 − 1.5× interquartile range (boxes) and Q3 + 1.5× interquartile range (whiskers).
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