Home › AP Statistics › Statistics › Confidence Intervals › In a group of 50 teens, 13 report more than 500 …
In a group of 50 teens, 13 report more than 500 Facebook friends. Using the plus-four method, x=15 and n=54, giving p' ≈ 0.278. For a 90% confidence level, z(0.05)=1.645 gives EBP ≈ 0.100. What is the resulting confidence interval?
A(0.178, 0.378)
B(0.078, 0.478)
C(0.278, 0.378)
D(0.000, 0.278)
Answer & Solution
Correct answer: A. (0.178, 0.378)
1. Using the plus-four sample, EBP = 1.645*sqrt((0.278)(0.722)/54) ≈ 0.100.
2. Lower bound: 0.278 - 0.100 = 0.178.
3. Upper bound: 0.278 + 0.100 = 0.378.
4. Option C only shifts p' upward instead of building a two-sided interval around it.
_Source: OpenStax Introductory Statistics (CC BY 4.0), Ch 8 "Confidence Intervals", section 8.3 A Population Proportion_
Related questions
A campus survey wants to estimate, with 95% confidence and a margin of error no greater thIn a Zogby poll of 48 respondents, nine rated a terrorist attack in their community as likOf 511 southern California homes surveyed for earthquake preparedness, 338 did NOT meet miContinuing the Field Poll example, p' = 0.79 from 400 of 506 surveyed. For a 90% confidencA Field Poll finds that 400 out of 506 surveyed California adults, about 79%, feel educatiAt the Ice Chalet, a randomly selected beginning skating class of 80 children has 64 girlsA poll of 1,200 voters finds 65% name the economy as the most significant election issue. A survey of 200 households finds that in 120 of them, the woman makes the majority of purc