Health Insurers and the Federal Government Are Both Putting Pressure

Health insurers and the federal government are both putting pressure on hospitals to shorten the average length of stay (LOS) of their patients. In 2003, the average LOS for non-heart patients was 4.6 days. A random sample of 20 hospitals in one state had a mean LOS for non-heart patients in 2008 of 3.8 days and a standard deviation of 1.2 days and is normally distributed. How large a sample of hospitals would we need to be 99 percent confident that the sample mean is within .5 days of the population mean?

A) 3
B) 7
C) 32
D) 48
E) 96