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.
Winters in Missouri can be long with temperatures ranging from mildly to bitterly cold. Kansas City's average January low is 26 Â°F (â3 Â°C) and St. Louis's average January low is 29 Â°F (â2 Â°C). The coldest temperature ever recorded in Missouri was â40 Â°F (â40 Â°C), set at Warsaw on 13 February 1905. Winter also tends to be the driest season, but typically yields significant amounts of winter precipitation. Snowfall averages 20 inches (51 cm) in the state's northern region, and 10 inches (25 cm) in the southeast.