Statistics Question

Question

A sample of size n=19 from a normal population. Find the critical value needed to construct a 95% confidence interval

Answer 1

If we knew the population standard deviation, we could use the z value of 1.96 corresponding to tail probabilities of 0.025, however since the population standard deviation is not given in the statement of this problem, we use the t value of 2.101 corresponding to 19-1 degrees of freedom and tail probabilities of 0.025.