I have a data set for a PhD paper in which I need to look for differences between 3 groups of observations. The issue is that ~95% are in one group and the rest are in the other two. The data table is attached below. Will any research on the differences between the three groups is valid from a formal statistical point of view?
group 1 group 2 1 402286 383596 2 8523 6107 3 15112 8535