Question

A study of 420,095 cell phone users found that 134 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 0.0328% for those not using cell phones. 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. __% < p < __%

Answer 1

Sample proportion = 134 / 420095 = 0.000319

90% confidence interval is

- Z * sqrt( ( 1 - ) / n) < p <   + Z * sqrt( ( 1 - ) / n

0.000319 - 1.6449 * sqrt(0.000319 * 0.999681 / 420095) < p < 0.000319 + 1.6449 * sqrt(0.000319 * 0.999681 / 420095)

0.000274 < p < 0.000364

0.0274% < p < 0.0364%