A medical researcher wants to investigate the amount of time it takes
for patients' headache pain 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 17 minutes. How large a sample should
she take to estimate the mean time to within 4 minutes
with 91% confidence?
Sample Size =