For the accompanying screen display, a simple random sample of size n = 40 was obtained from the population of duration times (seconds) of eruptions of the old Faithful geyser.
a. What is the number of degrees of freedom that should be used for finding the critical value ta/2?
b. Find the critical value ta/2corresponding to n = 40 and a 95% confidence level.
c. Give a brief general description of the number of degrees of freedom.