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.
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.