Question

an article describes several studies of the failure rate of defibrillators used in the treatment of heart problems. In one study conduced by the Mayo Clinic, it was reported that failures were experienced within the first 2 years by 18 of 89 patients under 50 years old and 19 of 367 patients age 50 and older who recieved a particular type of defibrillator. Assume it is reasonable to regard these two samples as representative of patients in the two age groups who recieve this type of defibrillator.

a) construct a 95% confidence interval for the proportion of patients under 50 years old who experience a failure within the first 2 years after recieving this type of defibrillator.(round answers to three decimal places.

(_________ , _________)

b) Construct a 99% confidence interval for the proportion of patients age 50 and older who experience a failure within the first 2 years after recieving this type of defibrillator. (round answers to three decimal places)

(_________ , _________)

c) Suppose that the researchers wanted to estimate the proportion of patients under 50 years old who experience a failure within the first 2 years after recieving this type of defibrillator to within 0.03 with 95% confidence. How large a sample should be used? Use the results of the study as a preliminary estimate of the population proportion. (enter answer as a whole number)

____________ patients

Answer 1

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