My DS7 is working on a project for the school science fair. He is testing the Stroop Effect, specifically the difference in times between kids and adults. He has done a great job collecting the data and has had fun learning how to use an Excel spreadsheet. Today though I tried to explain how he could get the "average" (mean) of each group. He understood the formula, in terms of adding all the numbers and dividing by the number of subjects. The adults had 16 subjects and the kids 15. So when he looked at the difference in means from each group, his conclusion was that the difference occurred because there was one less kid.
Do you know of any websites or other resources that do a good job of explaining this concept in a kid friendly way? Or is this just too high a level of concept and I shouldn't expect that he should get it? (He works at about a 3rd grade level in math and understands multiplication and division well. So far he's understood everything I've thrown at him.)
Thanks in advance for your help!
