How can a histogram be useful?
Just like stem-and-leaf plots, histograms show us shapes of distributions of the observations. If properly constructed, not too few or too many intervals, histograms allow us to determine whether the shape of our data distribution is bell-curved, right-skewed, left-skewed, or neither, based on the overall heights of the bars. Histograms are also useful in identifying possible outliers. If a histogram is symmetric around some value that value equals the average. Half the area under the histogram lies to the left of that value, and half to the right. Below you will find two examples of histograms for the same set of grades we first listed in the bar graph section above. We seldom use fewer than 6 or more than 15 classes; the exact number that should be used in a given situation depends on the number of measurements or observations we have to group. Each item (measurement or observation) goes into one and only one interval (category). We try to make the intervals cover equal ranges of val
