Using the data of prevalence rate by age group obtained at the Health Statistics Office, I have experimented with the three main types of chart namely: Line graph, Bar chart and Pie chart in order to be able the select the most appropriate chart which displays the data more effectively and which would be the easiest the viewer to interpret.
This line graph is not appropriate with this type of data as the data is not continuous even though the axes are well labelled the data is displayed above each data point on the graph. Line graph is more effective to show evolution or trend of a variable in a lapse of time and not suitable for grouped data.
Bar cart is one of the most common type of chart to display statistics. It consists of vertical or horizontal bars to compare a set of data. On one axis there is the category (in this case age group) and on the other one shows a scale for discrete values (% of prevalence rate). The height of each bar is directly proportinal to its value assigned to it.
As it can be seen the data is well displayed using bar chart. All data are clearly visible and not confusing. There is no loss of data as the value for each age group is displayed on the top of each column. Both axes are well labelled and their values clearly visible. The viewer can interpret the chart at one glance.
A pie chart consists of a number of sectors. Each sector illustrate a data which is proportional to the angle of the sector, therefore, the bigger the angle or size of the sector, the bigger is its value. Pie chart is an efficient way to compare a set of variable.
As in the previous example, there is no loss of data. All the data are clearly displayed. The chart is easy to interpret and easy to understand at a glance. Compare to bar chart, pie chart is more flexible in terms of design and can be illustrated in unconventional manner.