A pharmaceutical company makes tranquilizers. Researchers in a hospital used the drug on a random sample of nine patients. The effective period of the tranquilizer for each patient (in hours) was as follows: 2.7; 2.8; 3.0; 2.3; 2.3; 2.2; 2.8; 2.1; and 2.4. Construct a 95% confidence interval for the population mean length of time that the effect of the tranquilizer lasts, and explain in complete sentences what the confidence interval means