Suppose students want to determine whether the caffeine in a cup of regular coff
ID: 3204377 • Letter: S
Question
Suppose students want to determine whether the caffeine in a cup of regular coffee, consumed each morning before class, can improve the performance of a typical student on a statistics exam. Suppose all students in the 8am section are given the treatment (1 cup of coffee) and all students in the 9am section are not permitted to have any caffeine before class. It turned out that students in the 9am section did better on the exam. This is not a well-designed study. Explain why "confounding" makes it difficult to draw conclusions about the effect of caffeine on students' exam performance from this study. (Identify a potential confounding variable.)Explanation / Answer
A potential confounding variable is the section (due to the different timings of the sections)
The class for the 9 am section starts one hour after the class for the 8 am section.
This means that there is a possibility that the students in the 9 am section are getting more sleep than students in the 8 am section. It is also possible that the students in the 9 am section are getting more time to do physical exercise than students in the 8 am section.
The additional such activities that the students in 9 am section engage in may contribute to their performance.
The students in 8 am section do not get the opportunity to engage in those activities.
Therefore, the set of drivers for the performance for the 8 am section students would be different from that of 9 am section students.
It is not only the intake of caffeine, but other factors (that are unaccounted for) that vary for the two section students. These factors independetly impact performance.
Therefore, The confounding produced by experiment with caffeine only for 8 am section while comparing with a 9 am section makes it difficult to draw conclusions about the effect of caffiene on student performance in exam.
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