Hint(s) Check My Work Wall Street Journal reported on several studies that show massage therapy has a variety of health benefits and it is not too expensive. A sample of 10 typical one-hour massage therapy sessions showed an average charge of $57. The population standard deviation for a one-hour session is o = $5.5. a. What assumptions about the population should we be willing to make if a margin of error is desired? The population is at least approximately normal is required b. Using 95% confidence, what is the margin of error (to 2 decimals)? 3.41 c. Using 99% confidence, what is the margin of error (to 2 decimals)