Multiple Box-Whisker Plots

The variables tribromomethane, dibromochloromethane, bromodichloromethane, tri-chloromethane, and tetrachloromethane do not differ between the sampling locations, the groups. Others, trichloroethene and tetrachloroethene have maximum concentrations in groups 4 and 5 of the river section. But this visual assessment is not very rigorous. 

Relationships between variables, which can be expressed as correlations, or relationships between the groups cannot be detected. Multivariate statistical methods must therefore be applied. 

The visual estimation of differences between groups of data has to be proved using multivariate statistical methods, as for example with multivariate analysis of variance and discriminant analysis (see Section 5.6). 

Graphical methods in connection with pattern recognition algorithms, i.e. geometrical or statistical methods, e.g. minimum spanning tree or cluster analysis, are more powerful methods for explorative data analysis than graphical methods alone. 

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Fig. 5-11. Multiple box-whisker plot of halogenated volatile hydrocarbons in river water at five different sampling locations...

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