10.2 Researchers at a National Weather Center in the northeastern United States recorded the number of 90 degree days each year since records first started in 1875. The numbers form a normal shaped distribution with a mean of = 9 and a standard deviation of = 2.5. To see if the data showed any evidence of global warming, they also computed the mean number of 90 degree days for the most recent n = 4 years and obtained M = 11.7 days. Do the data indicate that the past four years have had significantly more 90 degree days than would be expected for a random sample from this populaton? Use a one-tailed test with alpha = .05. (Note: Be sure and show a diagram of the research design. Also show all steps and calculations you made for each test following the process outlined in the z-test formula sheet handout. What statistical decision do you make in each case