We considered the differences between the temperature readings in January 1 of 1968 and 2008 at 51 locations in the continental US in Exercise 5.19. The mean and standard deviation of the reported differences are 1.1 degrees and 4.9 degrees respectively. Required:
a. Calculate a 90% confidence interval for the average difference between the temperature measurements between 1968 and 2008.
b. Interpret this interval in context.
c. Does the confidence interval provide convincing evidence that the temperature was higher in 2008 than in 1968 in the continental US? Explain.