The study involves dependent samples because it involves a before and after study which according to Lind et al., 2020, is the comparison of the measurements of a variable of interest before and after a certain event or condition in a study sample where the goal is to determine the difference between these two measurements.

The best statistical test to use would be the dependent sample t-test and this is so because the dependent t-test looks at two groups that are somehow related to each other by comparing the average values of these groups to see if there is a significant difference between them in different situations, also because, it helps to determine more accurately how the coffee affects the driving speeds of the drivers.

References

Lind, D. A., Marchal, W. G., & Wathen, S. A. (2020).Statistical Techniques in Business & Economics. McGraw-Hill Education.

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