number of students in training, broken into three groups: total in
training, total in OJT, and total in formal school.
Three variable curve chart
(3) Step curve chart (figure 1-28): When the data has abrupt
changes, you would use this type of curve chart to present it. However,
there are two disadvantages to using this type of chart.
change in the line causes it to lose the trend or feeling of movement
through time. The second disadvantage is when plotting two or more lines
on the same chart, they may cross or fall on the same vertical or
horizontal grid. This often confuses the reader and the chart loses its
effectiveness. When using this Chart to present data, you must ensure
that the reader can readily understand and evaluate the data the chart