Given these assumptions, we know the following. 1  The expected value of the difference between all possible sample means is equal to the difference between population means. 2  Thus, E(x 1 - x 2) = Î¼ d = Î¼ 1 - Î¼ 2. 3  The standard deviation of the difference between sample means (Ï d) is approximately equal to:
Guide to Joplin weather in December. The average maximum daytime temperature in Joplin in December is a cool 8Â°C (46Â°F). The average night-time temperature is usually a very cold -3Â°C (27Â°F). There are usually 5 hours of bright sunshine each day, which represents 51% of the 10 hours of daylight.
The twisterâs winds were estimated to be more than 200 mph, making the tornado an EF-5 on the Enhanced Fujita Scale, which measures a tornadoâs intensity. It devastated the city of 50,000, killing 161 and injuring more than 1,000. The Joplin tornado was the first single tornado in the U.S. to result in more than 100 fatalities since a tornado struck Flint, Mich., in 1953. Tornado damage in Joplin, Mo. Credit: National Weather Service.