Perry is trying to solve the following riddle: "what creature walks first on four legs, then two, then three? " he repeatedly tries to think of an animal that might walk on three legs, but he can only think of animals that walk on either two or four legs. finally, he is told the correct a human being, who crawls, then walks, then walks with a cane. which one of the following is the most likely explanation of perry’s difficulty?

The authors of the paper "fudging the numbers: distributing chocolate influences student evaluations of an undergraduate course"† carried out a study to see if events unrelated to an undergraduate course could affect student evaluations. students enrolled in statistics courses taught by the same instructor participated in the study. all students attended the same lectures and one of six discussion sections that met once a week. at the end of the course, the researchers chose three of the discussion sections to be the "chocolate group." students in these three sections were offered chocolate prior to having them fill out course evaluations. students in the other three sections were not offered chocolate. the researchers concluded that "overall, students offered chocolate gave more positive evaluations than students not offered chocolate." indicate whether the study is an observational study or an experiment. give a brief explanation for your choice.