Over half of all American teens (ages 12 to 17 years) have an online profile on at least one social media platform. A random sample of 487 teens with profiles found that 385 included photos of...

1. Over half of all American teens (ages 12 to 17 years) have an online profile on at least one social media platform. A random sample of 487 teens with profiles found that 385 included photos of themselves.

a. Estimate with 95% confidence the true proportion of teens with online profiles that include photos of themselves.

b. Is it plausible that the true proportion of American teens with profiles who have posted photos of themselves is 0.76?