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 needed so that the confidence interval will have a margin of error of 0.077? Write only an integer as your answer. Your Answer: getting better. A Gallup poll taken in July 2010 estimates this proportion to be 0.33. Using this estimate/what sample size is Answer Save Question 12 (1.5 points) 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 0.031 ? Write only an integer as your answer. Your Answer: Answer Save

Explanation / Answer

Question 11

Margin of error = Critical Test Statistic * Standard error of the proportion

Proportion that economic condition are better = 0.33

Standard error of the proportion = sqrt [p * (1-p)/ N]

so Margin of error = 0.077

Critical Test Statistic = 1.96

0.077 = 1.96 * sqrt [p * (1-p)/ N]

sqrt [p * (1-p)/ N] = 0.0393

p * (1-p)/ N = 0.001543

N = 0.33 * 0.67/ 0.001543 = 143

Question 12

Here as the proportion of children who watch squarepants is not given. So, we take it is p = 0.5

Margin of error = Critical Test Statistic * Standard error of the proportion

0.031 = 1.96 * sqrt [0.5 * 0.5/ N]

N = 1000

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