Question 11 (1.5 points) A pollster wants to construct a 95% confidence interval

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Question 11 (1.5 points) A pollster wants to construct a 95% confidence interval for the proportion of adults who believe that economic conditions are getting better. A Gallup poll taken in July 2010 estimates this proportion to be 0.33. Using this estimate, what sample size is needed so that the confidence interval will havea margin of error of 0.084? Write only an integer as your answer. Your Answer: Answer Save Question 12 (1.5 points)D A pollster wants to construct a 95% confidence interval for the proportion of children who watch Spongebob Squarepants. Estimate the sample size needed so that the confidence interval will have a margin of error of 0.021? Write only an integer as your answer.

Explanation / Answer

Answer 11

we have p = 0.33, margin of error (ME) = 0.084 and z score for 95% confidence level using normal distribution table is 1.96

using the formula

sample size(n) = p*(1-p)[z/ME]^2

setting the given values, we get

n = 0.33*(1-0.33)*[1.96/0.084]^2 = 0.33*0.67*544.44 = 120.377

Rounding to nearest integer, we get sample size = 120

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