Question

Over half of all American teens (ages 12 to 17 years) have an online profile, mainly on Facebook. A random sample of 494 teens with profiles found that 300 included photos of themselves.

(a) Give the 90% large-sample confidence interval for the proportion p of all teens with profiles who include photos of themselves. Large-sample Interval: to

(b) Give the plus four 90% confidence interval for p . (The plus-four interval always pulls the results away from 0% or 100%, whichever is closer. Even though the condition for using the large-sample interval is met, the plus four interval is more trustworthy.) Plus four Interval: to

Answer 1

(a)

(b)

p = 0.6064

plugin values we get E = 0.0361

confidence interval is

c.i = 0.6064-0.0361 < P < 0.6064+0.0361 = 0.5703 to 0.6425