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What is the non parametric alternative to ANOVA?
The Kruskal–Wallis test by ranks, Kruskal–Wallis H test (named after William Kruskal and W. Allen Wallis), or one-way ANOVA on ranks is a non-parametric method for testing whether samples originate from the same distribution. It is used for comparing two or more independent samples of equal or different sample sizes.
Is ANOVA necessary?
ANOVA is helpful for testing three or more variables. It is similar to multiple two-sample t-tests. However, it results in fewer type I errors and is appropriate for a range of issues. ANOVA groups differences by comparing the means of each group and includes spreading out the variance into diverse sources.
Can you do one way ANOVA with raw data?
One-way ANOVA would definitely be the way to go, however upon conducting normality tests on my data, heteroskedascity seems to the main issue. My raw data, without any transformation, produced a ratio of variances ( F max = 19.1) which is very much higher than the critical value ( F c r i t = 4.16) and therefore I cannot perform one-way ANOVA.
When to use ANOVA to compare two samples?
We can use ANOVA to prove/disprove if all the medication treatments were equally effective or not. Another measure to compare the samples is called a t-test. When we have only two samples, t-test and ANOVA give the same results.
Which is better weighted least squares or unweighted ANOVA?
This yields slightly different F and p -values than the unweighted ANOVA ( 4.5089, 0.01749 ), but it has addressed the heterogeneity well: Weighted least squares is not a panacea, however. One uncomfortable fact is that it is only just right if the weights are just right, meaning, among other things, that they are known a-priori.
When to reject the null hypothesis in ANOVA?
Another measure for ANOVA is the p-value. If the p-value is less than the alpha level selected (which it is, in our case), we reject the Null Hypothesis. There are various methods for finding out which are the samples that represent two different populations. I’ll list some for you: