Atticus pushed his glasses to his forehead; they slipped down, and he dropped them in the street. In the silence, I heard them crack. Atticus rubbed his eyes and chin; we saw him blink hard. In front of the Radley gate, Tim Johnson had made up what was left of his mind. He had finally turned himself around, to pursue his original course up our street. He made two steps forward, then stopped and raised his head. We saw his body go rigid.

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.