In a 2018 study reported in The New England Journal of Medicine, Halpern et al. randomly assigned smokers to one of five groups, including four smoking cessation interventions and usual care. Usual care consisted of access to information regarding the benefits of smoking cessation and to a motivational text-messaging service. The four interventions consisted of usual care plus one of the following: free cessation aids such as nicotine-replacement therapy or pharmacotherapy, free e-cigarettes, free cessation aids plus $600 in rewards for sustained abstinence, or free cessation aids plus $600 in redeemable funds deposited in an account for each participant, with money removed from the account if cessation milestones were not met. Researchers measured the percentage in each group who sustained smoking abstinence for six months. Results indicate that financial incentives added to free cessation aids resulted in a higher rate of sustained smoking abstinence than free cessation aids alone. Is this study an observational study or a controlled experiment? Explain.

a. Is this study an observational study or a controlled experiment? Explain.

b. Identify the treatment and response variables.

c. Can a cause-and-effect conclusion be drawn from this study? Why or why not?