It is a type of graph in which three curves are drawn which appears somewhat in the shape of the letter Z. For this reason the graph is known as Z Curve.
The three curves drawn are:
- Curve of original data
- Curve of cumulative data
- Moving total curve which is plotted from the moving annual total, if figures are monthly or weekly. If the figures are not monthly or weekly, but daily then the curve is plotted from moving monthly totals.
A pictograph is a symbol representing a concept, object, activity, place or event by illustration. It is a form of writing in which ideas are transmitted through drawing. To convey statistical information pictograms uses picture symbols. Pictographs should have to be used carefully because the graphs may, either accidentally or deliberately, misrepresent the data. That is why a graph should be visually accurate. Pictographs are the most important means of hazard communication to emergency responders (police, fire service, ambulances) because they can always be found on transport units at incident sites. Pictograms are often used in newspapers as they are more eye catching than ordinary bar charts.