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.
In Joplin, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year. The clearer part of the year in Joplin begins around June 10 and lasts for 4.8 months, ending around November 3.