Besides the central tendency and spread of the data, the shape of the histogram can also be of
interest. For example, Figure 9 shows a bi-modal distribution. This indicates that the
measurements are not from a homogeneous process, since there are two peaks indicating two
central tendencies. There are two (or more) factors that are not in harmony. These could be two
machines, two shifts, or the mixed outputs of two suppliers. Since at least one of the peaks must
be off target, there is evidence here that improvements can be made.