I have a population of colorectal polyps, divided in 3 groups by size: 1-3 mm, 1-5 mm, 1-10 mm. So, each group contains the subjects from the smaller group.

No, I want to compare the proportion of X characteristic (binary) among these groups.

It seems that chi test is not enough as the subjects are overlapping among these groups.

Which test do you think is appropriate for comparing proportions between these groups?

Thanks.