A study of 420052 cell phone users found that 139 of them de

A study of 420,052 cell phone users found that 139 of them developed cancer of the brain or nervous system. Prior to this study of cell phone use, the rate of such cancer was found to be 0.0245% for those not using cell phones. Complete parts (a) and a. Use the sample data to construct a 90% confidence interval estimate of the percentage of cell phone users who develop cancer of the brain or nervous system. (Round to three decimal places as needed.) b. Do cell phone users appear to have a rate of cancer of the brain or nervous system that is different from the rate of such cancer among those not using cell phones? Why or why not? A. No, because 0.0245% is not included in the confidence interval. B. No, because 0.0245% is included in the confidence interval. C Yes, because 0.0245% is included in the confidence interval. D. Yes, because 0.0245% is not included in the confidence interval.

Solution

Sample size = 424052

Devloped cancer = 139

sample proportion= 0.000328 = 0.0328%

Population proportion = 0.0245% (given)

For 90% z value = 1.64

Margin of error = 1.64(sigma)/rt 420052

As sample size is very large margin of error is almost 0

Hence we get p as (0.03, 0.04)

b) No because 0.0245% is not included in the confidence interval

Confidence interval for sample proportion =