Biologists studying the healing of skin wounds measured the rate at which new cells closed a cut made in the skin of an anesthetized newt. Here are data from a random sample of 18 newts, measured in micrometers (millionths of a meter) per hour: 29, 27, 34, 40, 22, 28, 14, 35, 26, 35, 12, 30, 23, 18, 11, 22, 23, 33 (a) Create a QQ plot of the data. Do you think it is reasonable to assume that the population distribution is normal? Explain your answer. (There isn’t a unique "right" answer.) (b) Regardless of your answer to (a), assume the population distribution is normal and use that assumption to create a 90% CI for µ. (Use a calculator to find ¯x and s and then use the formula provided in class to prepare for exams. Then check your answer with R if you wish.) (c) Suppose the problem statement included the addition, "Prior experience in the lab indicates that the population standard deviation is close to σ = 8 (micrometers per hour)." This would call for which changes to your confidence interval calculation? Write down the letters of all that are correct. i. Replace ¯x with x¯ n . ii. Replace t17,.05 with z.05 = 1.645. iii. Replace √ n with n. iv. Replace s (calculated from the data) with σ = 8. v. Replace s (calculated from the data) with √σ n = √ 8 18 .