Find the critical value for a 0.99 confidence level for a t-distribution with a sample size n = 19

2. Total plasma volume is important in determining the required plasma component in blood replacement therapy for a person undergoing surgery. Plasma volume is influenced by the overall health and physical activity of an individual.

Suppose that a random sample of 45 female firefighters are tested and that they have a plasma volume sample mean of = 36.2 ml/kg and the population has a standard deviation of = 7.37 ml/kg. Let be the population mean plasma volume for female firefighters.

a) What is the value of for a 95% confidence interval?

b) What is the value of E?

c) Find a 95% confidence interval for .

3. A teacher is curious about the amount of studying time students dedicate to the final exam of a particular stats course. A sample of 21 students is taken, and it is found that the mean study time for this sample was x = 109 minutes, and the sample standard deviation was = 17.1 minutes. Let be the mean study time (in minutes) of the entire population of students writing this stats exam.

a. What is the value of for a 98% confidence interval?

b. What is the value of ?

c. Find a 98% confidence interval for .