In 2009, a law was passed in New Zealand banning the use of handheld cell phones while driving. In 2012, researchers wanted to determine if a smaller proportion of drivers use handheld cell phones now that the law was in effect. To find out, data collectors stood at the side of three streets in Wellington, New Zealand, and recorded the proportion of drivers who drove by while talking on their handheld cell phones. By referring to a 2006 study, the researchers obtained the proportion of drivers in Auckland, New Zealand, who talked on handheld cell phones while driving before the law. They concluded that the proportion of drivers who use handheld cell phones while driving has decreased since the law was passed.
a. Is such a study an experiment or an observational study? Explain.
b. What are the explanatory and response variables?
c. What is the conclusion of the study? Does this mean there is causality or only an association between the two variables? Explain.
d. Were the 2006 and 2012 studies performed in the same city? Why might this be a problem?
e. How many years apart were the two studies? Why might this be a problem?