A large study of heart disease that included White and African-American participants considered the age and gender of the participants but not their socioeconomic status. The conclusion drawn by the researchers was that being an African American male places you at greater risk for heart disease than being a White male. The problem with this conclusion is

What percentage of roads in germany have no speed limit?

What are the state's top three naturally produced minelars?

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.