A popular weight loss program claims that with its recommended healthy diet regimen, users lose significant weight within a month. In order to estimate the mean weight loss of all customers, a nutritionist takes a sample of 18 dieters and records their weight loss one month after joining the program. He computes the sample mean and the standard deviation of weight loss as 12.5 pounds and 9.2 pounds, respectively. He believes that weight loss is likely to be normally distributed.
a. Calculate the margin of error with 95% confidence.
b. Compute the 95% confidence interval for the population mean.