Posted by Anonymous on Monday, December 10, 2012 at 5:33pm.
We take a simple random sample of 100 people and check their ages. Out of the 100, 15 are 65. What is the probability that the proportion of people over 65 in the entire population is between 13% and 17%? What error range can we guarantee with 90% certainty?

statistics  MathGuru, Monday, December 10, 2012 at 8:13pm
Use the normal approximation to the binomial distribution.
mean = np
sd = √npq (where q = 1p)
Therefore:
mean = 100 * .15 = 15
sd = √npq = √(100 * .15 * .85) = 3.57
Use zscores:
z = (13  15)/3.57 = 0.56
z = (17  15)/3.57 = 0.56
Use a ztable to find the probability between the two zscores.
For the second part, use a 90% confidence interval formula.
I hope this will help get you started.
Answer This Question
Related Questions
 statistics  A specific study found that the average number of doctor visits per...
 statistics  A specific study found that the average number of doctor visits per...
 Statistics  1. A study of 40 people found that they could do on the average15 ...
 Statistics  People end up tossing 12% of what they buy at the grocery store (...
 statistics  People end up tossing 12% of what they buy at the grocery store (...
 statistics  People end up tossing 12% of what they buy at the grocery store (...
 statistics  Starting with a population that is normally distributed with a mean...
 statistics  One of the ways most people relieve stress is to reward themselves ...
 college  Essentials of statistics is the subject and the question is: The ...
 Statistics Emergency please  People end up tossing 12% of what they buy at the ...
More Related Questions