When the drawings are complete, ask them to meet with another group and compare their products. Contact a grade one teacher and ask whether you can survey the members of her class with respect to the same traits. Repeat this for a grade 11 class. Possible traits are shoe size, little finger length, wrist circumference, pulse rate, and eye colour. Record the sex of each participant in the survey.
Bar graphs are one way to compare variability of traits.
You will have to make a decision on how you are going to gauge the variability in each characteristic. Repeat this process for the other grades you have surveyed. Identify other questions to guide analysis of your data. On a chart, list characteristics which are variable in one column and those which are invariable in the other. For instance, eye colour would go in the variable column and two arms in the invariable column.