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 est

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 2 minutes with 93% confidence?