Electronic cigarettes 2013 In a 2013 randomized controlled study in New Zealand, patients who wanted to quit smoking were randomly assigned to smoke e-cigarettes that deliver nicotine, to use a nicotine patch, or to use a placebo e-cigarette that does not deliver nicotine. The e-cigarette group had a lower rate of quitting than expected by the researchers: 21 of 289 quit smoking.

a) Write a 95% confidence interval and interpret it in context.

b) If researchers want to determine the level of abstinence

(quitting smoking) for e-cigarettes to within 1.5 percentage points, how many subjects should get that treatment?