Researchers at a National Weather Center in the northeastern US recorded the number of 90 degree days each year since records first started in 1875. The numbers for a normal shaped distribution with a mean of mu=9.6 and a standard deviation of sigma=1.9

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=12.25. 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 population? Use a one-tailed test with alpha=0.05