One way to examine this question might be to perform a non parametric test for independence between the units and sub levels. using the excavation units as one variable (group the k#s, l#s, and m# units together) and sub levels as the second variable (i. e. form a 3 x 2 table) test the idea that units and sub levels are independent of each other.

c) the critical values (or probabilities) involved, and
d) which tables (if any) were consulted,
e) the calculated test statistic
f) whether the null hypothesis is rejected, or not rejected.