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.
JOPLIN, Mo. â The sun shone for the first time in days on this devastated city on Tuesday, illuminating the full extent of the damage as rescue workers performed the grim task of searching for survivors and victims in buildings leveled by the United States â deadliest tornado since modern record-keeping began.