Answer to Question #134584 in Statistics and Probability for Aliyah Alladin

Question

A medical researcher wants to investigate the amount of time it takes for patients’ headache to be relieved after taking a new prescription painkiller. She plans to use statistical methods to estimate the mean of the population of relief times. She believes that the population is normally distributed with a standard deviation of 20 minutes. How large a sample should she take to estimate the mean time tow within 1 minute with 90% confidence

Answer 1

n = [z*s/E]^2

Z at 90% confidence is = 1.645 ( From Standard Normal Table )

n = (1.645 *20/1)² = 1082 when rounded up