Question

Question 9 (1.5 points) A medical researcher wants to construct a 99% confidence interval for the proportion of knee replacement surgeries that result in complications. An article in the Journal of Bone and Joint Surgery suggested that approximately 8% of such operations result in complications. Using this estimate, what sample size is needed so that the confidence interval will have a margin of error of o.023 2 Write only an integer as your answer. Your Answer Answet Save Question 10 (1.5 points) A researcher wants to construct a 99% confidence interval for the proportion of people who changed jobs in the past year What sample size is needed so that the confidence interval will have a margin of error of 0.031 7 Write only an integer as your answer. Your Answer; Answer Save 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 o.33. Using this estimate, what sample size is needed s?that the confidence interval will have?margin of error of 0.026 ? Write only an integer as your ansver Your Answers

Answer 1

9 ) Determination of sample size necessary for estimating population proportion :

$n=\left ( \frac{Z}{E} \right )^2\times p(1-p)$

where ,

Required sample size :

$n=923.24\approx 924$

10 ) Determination of sample size necessary for estimating population proportion :

$n=\left ( \frac{Z}{E} \right )^2\times p(1-p)$

where ,

Required sample size :

$n=1726.27\approx 1727$

11 ) Determination of sample size necessary for estimating population proportion :

$n=\left ( \frac{Z}{E} \right )^2\times p(1-p)$

where ,

Required sample size :

$n=1256.48\approx 1257$