Amedical 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 15 minutes. how large a sample should she take to estimate the mean time to within 3 minutes with 90% confidence?

9.4.34  question   to estimate the height of a stone  figure, an observer holds a small square up to her eyes and walks backward from the figure. she stops when the bottom of the figure aligns with the bottom edge of the  square, and when the top of the figure aligns with the top edge of the square. her eye level is 1.811.81 m from the ground. she is 3.703.70 m from the figure. what is the height of the figure to the nearest hundredth of a  meter?