I apologize for the delay in responding. It looks like you have very interesting results, and it's okay if your hypothesis was not supported.
One way to tell if the girls and boys were different is to do a t test
). This is a simple statistical test that you can do in Microsoft Excel (with the Add-in called Analysis Toolpak). Organize your data by gender, with one column for girls and one column for boys. If someone saw the gorilla, he/she gets a "score" of 1. If someone did not see the gorilla, he/she gets a "score" of 0. Then you can compare the two groups to see whether they are different. I ran a quick test, and it does not look statistically different. However, there is another important factor: whether they counted right.
If someone counted the right number of passes AND saw the gorilla, that person gets a score of 2. If someone saw the gorilla but counted the wrong number of passes, you could give that person a score of 1. If someone counted the right number of passes but did not see the gorilla, that person would also score 1. If someone missed the gorilla and counted the wrong number of passes, that person gets a score of 0. You could try comparing people that way to see how gender and age affected their attention.
You may not have to use statistics (though it certainly impresses the judges at this level). You could visualize your data by making bar graphs. Again, I think it's important that you look at 4 groups: (1) people who saw everything, (2) people who missed the gorilla because they were busy counting, (3) people who saw the gorilla but messed up the counting, and (4) people who missed the gorilla and miscounted. You could compare these by gender and by age. The age is difficult to analyze, but doing a bar graph by age could be interesting.
Here is the Science Buddies information for data analysis and graphs: http://www.sciencebuddies.org/science-f ... ysis.shtml
Let me know if this makes sense, and definitely write again if you have more questions.