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Statistical Advisor, How To Compare Several Variables or Repeated Measures

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GENERAL LINEAR MODELS (GLM): This chapter discusses so-called analysis of variance (ANOVA). ANOVA is used, among other applications, for simultaneously comparing means in several groups or for several variables. The latter application is referred to as repeated measures ANOVA, because one simultaneously compares repeated measurements on the same subjects (or observations). ANOVA assumes that the variables in the comparison are normally distributed. The ANOVA/MANOVA chapter also discusses repeated measures ANOVA/MANOVA analyses.

NONPARAMETRICS & DISTRIBUTIONS: This chapter describes so-called nonparametric tests for comparing variables or repeated measurements. The most commonly used test is the Friedman analysis of variance. This test should be used if one is not sure of the distribution of the variables used in the comparison. For example, the data may actually consist of rankings rather than precise measurements.

GRAPHICAL ANALYTIC TECHNIQUES: Graphical analytic techniues include numerous facilities for producing histograms, line graphs, scatterplots, etc., simultaneously for more than one variable. These graphs offer a wide variety of methods to visualize differences between variables.