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.
Satellite image from May 22nd at 6:15 ET showing the supercell thunderstorm that the Joplin tornado formed from. (NASA) On May 22, 2011 the city of Joplin, Missouri was impacted by an EF-5 tornado. There were 158 deaths with over a thousand injured as a result of the tornado. At its peak it was up to a mile wide with winds in excess of 200 miles per hour. The tornado was on the ground for 22.1 miles and lasted an estimated 38 minutes from start to finish.