Suppose you calculate a mean of a population and you want to know how representative that mean is of a random data point in that population. In other words, is the data bunched tightly around the mean, or is it more loosely distributed over the possible range of values? An example would be high temperatures in July versus high temperatures in April or October. In general, the highs in April and October will vary more widely from the means in those months than the highs in July.
In summary, it takes not only the mean to adequately describe a population, but there must be some way to measure the dispersion, or distribution, of the data around the mean.
1. Find what is called the distribution of a data population
2. Find the statistic that measures the width of dispersion of the population data about its mean.
Give an example of the type of situation where this statistic might be critical to making good decisions about the population under study.
This explains variance and standard deviation.