2.30 Stopping traffic with a smile! Throughout Europe, more than 8000 pedestrians are killed each year in ro accidents, with approximately 25% of these dying when using a pedestrian crossing. Although failure to stop for pedestrians at a pedestrian crossing is a serious traffic offense in France, more than half of drivers do not sron when a pedestrian is waiting at a crosswalk. In this ex periment, a female research assistant was instructed to stand at a pedestrian crosswalk and stare at the driver's face as a car approached the crosswalk. In 400 trials, the research assistant maintained a neutral expression, and in a second set of 400 trials, the research assistant was instructed to smile. The order of smiling or not smiling was randomized, and several pedestrian crossings were used in a town on the coast in the west of France. Re- search assistants were dressed in normal attire for their age (jeans/T-shirt/trainers/sneakers).23 (a) In the 400 trials in which the assistant maintained a neutral expression, the driver stopped in 229 out of the 400 trials. Find a 95% confidence interval for the proportion of drivers who would stop when a neutral expression is maintained. p) In the 400 trials in which the assistant smiled at the driver, the driver stopped in 277 out of the 400 tri- als. Find a 95% confidence interval for the propor- tion of drivers who would stop when the assistant is smiling