Question

1. Researchers at a National Weather Center in northeastern United States recorded the number of 90 degree days each year since records first started in 1875. The numbers form a normal distribution with a mean of u = 9.6 and a standard deviation of 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 an alpha level of .05.

Answer 1