A conservation biologist stationed in St. John's, Newfoundland has been researching thelifespan of local avian wildlife. Specifically, they have recently focused on puffins. In a recent study, based on a random sample of 21 puffins, they reported the 99% confidence interval for the average lifespan to be (5.974, 8.236). Assume puffin lifespan follows a normal distribution.
What is the critical value used in this confidence interval?
What is the sample mean from this sample?