A survey was conducted on 218 undergraduates from Duke University who took an in

Question

A survey was conducted on 218 undergraduates from Duke University who took an introductory statistics course in Spring 2012. Among many other questions, this survey asked them about their GPA and the number of hours they spent studying per week.

Is this an experiment or an observational study?

The survey showed that people who studied more had higher GPAs. Can we conclude that studying for a longer time will cause a higher GPA? Explain your reasoning.

What is the response variable for this study? What is the explanatory variable?

Explanation / Answer

This is an instance of observational study. Here, the surveyeor, observes the subjects (undergraduates) and measures her variable of interest (GPA) to study relationship betwen GPA and number of hours. No treatments have been assigned on subjects that is no manipulation of variables had been done.

The observational study definitely gives an idea, provided data were taken for large number of samples over a long period and then suitably studied and interpreted. But, since only 218 samples had been used for the study and only during Spring 2012 semester had been used as the duration so conclusion is not robust.

The response variable is the dependent one. Here, it is GPA. Explanatory variable is the independent variable and it is hours spent in studying per week.

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