What are the rules that you want to follow to determine the boundaries of the groups?
- Is group 1 always the numbers less than 9 and group 2 is everything else?
- Is group 1 always the first half of the data and group 2 the second half?
- Do you divide the data into groups that each contain 8 elements?
- Do you divide the data into groups based on the smallest multiple of 8 that they are less than or equal to?
Each of those four rules would divide the sample data set you showed into the groups you showed but they could behave very differently on other data sets. You tell us how to define the bins and we likely can show you how to figure out into which bin each element belongs.
