Contents
Can you use ANOVA on percentages?
There is a strongly emerging consensus that you cannot analyze percentage data with ANOVA. The arcsine square root transformation has long been standard procedure when analyzing proportional data in ecology, with applications in data sets containing binomial and non-binomial response variables.
What is a continuous predictor?
Continuous predictors. • Definition: Variables that can take on any value within a range. • Examples: age, income, family size, body mass.
Is it possible to analyze percentage data with Anova?
There is a more and more strongly emerging consensus that you cannot analyze percentage data with ANOVA. Some of the two latest references are Jaeger (2008) and Dixon (2008) the abstract of which I post below. Jaeger, T. F. (2008).
When to use beta regression instead of ANOVA?
If you choose to do an ordinary ANOVA on proportional data, it is crucial to verify the assumption of homogeneous error variances. If (as is common with percentage data), the error variances are not constant, a more realistic alternative is to try beta regression, which can account for this heteroscedasticity in the model.
Which is an example of a nonparametric one way ANOVA?
Your first example (with count data) could be approached using the Kruskal-Wallis test as a nonparametric analog of the one-way ANOVA, followed by Dunn’s test which is akin to performing rank sum tests based on the same rankings from the Kruskal-Wallis test, and using a pooled variance term based on rank sum distributions.
How are post drug values expressed in ANOVA?
Previously I have just expressed the post-drug values as a percentage of the pre-drug (not percentage difference), and then compared the mean percentages of the various different groups with a two-way ANOVA. (nb. the percentage data are normally distributed according to shapiro-wilks test)