New research suggests that children often learn coping skills from imaginary friends. In a study of 100 children done at the University of Oregon and reported in Developmental Psychology

(USA Today, December 20, 2004, “‘Pretend’ friends, actual benefits”), 33% of the children still had an imaginary friend at the age of 7. Find the 90%

confidence interval for the true proportion of “success”

for a binomial experiment with n  100 and an observed proportion of 0.33.