Boxplot including outliers in R, make the whole ranges being compared.

Question

I am comparing several values using R, they are 8 variables stored in 1000 length vectors. That means, 1000*8 matrix, 8 columns represent 8 variables.

Then I call

boxplot(test),

I got like: The mean values of 8 variables are very close to each other. Which makes the comparison and interpretation very hard. Can I include all the outliers in my plot ? Then the whole range would be easier to compare ? Or any other suggestions could be given to distinguish these variables ?

Answer 1

Here is the boxplot in question (since the OP doesn't have the rep to post pictures):

It looks like the medians (and likely also the means) are pretty much identical, but the variances differ between the eight categories, with category 1 having the lowest and 8 the highest variance. Depending on the real question involved, these two pieces of information (similar median/mean, different variance) may already be enough.

If you want a formal significance test whether the variances are equal, you can use Hartley's or Bartlett's test. If you want to formally test equality of means with unequal variances (so ANOVA is not appropriate), look here.