Question 8.138

41. Hospital Length of Stay. The U.S. Agency for Healthcare Research and Quality reports that the mean length of stay in the hospital for patients suffering from acute myocardial infarction (heart attack) was 4.8 days. Suppose a sample of 31 heart attack patients had a mean length of stay of 4.8 days, with a sample standard deviation of 3 days. Do the following:

  1. State how the conditions for the interval for are met.
  2. Find for a confidence interval with 95% confidence.
  3. Construct and interpret a 95% confidence interval for the population mean length of stay for all heart attack victims.

8.2.41

(a) We are not told that the population is normal. However, the sample size is large ( is ). (b) (c) (3.7, 5.9). We are 95% confident that μ, the population mean length of stay in hospital for all heart attack victims, lies between 3.7 days and 5.9 days.