In contrast, the histogram of Figure 10 shows a situation in which the spread of measurements is
lower on one side of the central tendency than on the other. These could be measurements of
miles per gallon attained by an automobile. There are many situations that decrease fuel
economy, such as engine settings, tire condition, bad weather, traffic jams, etc., but few
situations that can significantly improve it. The wider variance can be attacked by optimizing any
of the controllable factors such as tuning the engine, replacing the tires used, etc. Moving the
central tendency in the direction of the smaller variance is unlikely unless the process is radically
changed (e.g., reducing the weight of the vehicle, installing a new engine, etc.).