
250 ◾ Software Metrics
variation. However, if the data were to exceed the control limits, we would
take action to bring them back under control—that is, back within the band
between the upper and lower control limits. In this example, exceeding the
upper control limit means that too much preparation is being done, or not
enough time is being spent during inspection. If the value is below the lower
control limit, then not enough preparation is being done, or too much time
is being spent during inspection. Even when data do not exceed the con-
trol limits, action can be taken when the trend veers toward the edge of the
acceptable band, so t ...