### How to Find Confidence Interval and Perfrom One Tailed T Test

Let x be a random variable representing percetage of carboxyhemoglobin in the blood. For a person who is a regular heavy smoker, x has a distribution that is approximately normal. A random sample of n= 12 blood test given to a heavy smoker gave the following results: 9.1 9.5 10.2 9.8 11.3 12.2 11.6 10.3 8.9 9.7 13.4 9.9 a