A pharmaceutical company makes tranquilizers. It is assumed that the distribution for the length of time they last is approximately normal. Researchers in a hospital used the drug on a random sample of 9 patients. The effective period of the tranquilizer for each patient (in hours) was as follows: 2.7; 2.9; 3.0; 2.3; 2.3; 2.2; 2.8; 2.1; and 2.4. NOTE: If you are using a Student's t-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.) Construct a 95% confidence interval for the population average length of time. (i) State the confidence interval. (Round your answers to two decimal places.) ( l , ) (ii) Sketch the graph. E: Q C.L,= 3=:] 2 2 NI (iii) Calculate the error bound. (Round your answer to two decima places.) :1