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:2.5;2.9;3.1;2.3;2.3;2.2;2.8;2.1; and2.4.

NOTE: If you are using a Student'st-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.)

What are the answers for the questions marked "x"?

Part (e) Construct a 95% confidence interval for the population mean length of time. (i) State the confidence interval. (Round your answers to two decimal places.) 2.25 2.77 (ii) Sketch the graph. 0.3 X C.L. = 0.95 0.3 X N 2.25 2.77 XPart (d) Which distribution should you use for this problem? (Enter your answer in the form z or toy where f is the degrees of freedom.) t af X