A study conducted in 2002 by Shiff man, Dressler, Hajeh, and Gilburt investigated whether a nicotine lozenge is helpful for smokers trying to quit smoking. The researchers recruited smokers who were interested in quitting through advertisements near four sites in the United Kingdom and 11 sites in the United States. Those smokers who met the screening qualifications were randomly assigned to one of two groups: One group received nicotine lozenges and the other group received placebo lozenges. The subjects were compared on various background variables at the beginning of the study, and at the end of the study they were compared on whether or not they successfully abstained from smoking. Of the 459 subjects in the nicotine group, 42.9% were male. Of the 458 subjects in the placebo group, 40.2% were male.
a. Is this an observational study or an experiment?
b. Produce a 2 × 2 table of counts to represent these data.
c. Create a relevant graph to display the data.
d. Comment on whether the percentages seem to suggest a strong association between sex of participant and treatment.
e. Conduct an appropriate theory-based test to investigate whether the percentages of males diff er significantly between the two groups. Report the test statistic and p-value and summarize your conclusion.
f. Do you think the researchers would be pleased with the result of this significance test. Explain why or why not.