Answer: Group percentages
Explanation: Employing group percentage should give in the survey would be best as it summarizes the the various divisions of a whole group of observation. It works by assigning a percentage of 100 to the entire group and then summarizing the number in each category of the group as a fraction of the entire group multiplied by 100.
In the scenario above, using group percentage, if the number of third and sixth graders are 30 and 40 respectively. While 15 and 10 third and sixth graders buys their lunch at school respectively. The group percentages will be ;
Third graders = 50% buys lunch at school while 50% don't.
Sixth graders = 25% buys lunch at school while 75% don't.