14. Researchers at a National Weather Center in the northeastern United States recorded the number of 90° Fahrenheit days each year since records first started in 1875. The numbers form a...

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Extracted text: 14. Researchers at a National Weather Center in the northeastern United States recorded the number of 90° Fahrenheit days each year since records first started in 1875. The numbers form a normal-shaped distribution with a mean of u = 9.6 and a standard deviation of o = 1.9. To see if the data showed any evidence of global warming, they also computed the mean number of 90° days for the most recent n = 4 years and obtained M = 12.25. Do the data indicate that the past four years have had signifi- cantly more 90° days than would be expected for a random sample from this population? Use a one- tailed test with a = .05.