1. When is it best to use a pie chart: It is best to use a pie chart when there is a categorical variable such that the slices of pie chart will represent values of each category. Hence, it is useful when various category values represent composition of something, for example, market share of an industry. The pie chart can be used to represent only a single set of data with no negative values. Ideally, if there are more than 7-8 observations, pie chart should not be used as it is tough to distinguish the slices visually (Few, 2007).
2. When is it best to use a bar graph: A bar graph can be used to compare various datasets or various time periods for same data. The data can be positive or negative and bar graph can be horizontal or vertical. It gives the maximum and minimum values visually and also helps to understand the concentration of data (Yi & Sapountzis, 2019).
3. When is it best to use a line graph: Line graph is usually used to present continuous data. A line graph is most useful to pick trends or patterns in the data. For example, stock price during a period. It can also be used to study large changes over long period of time. For example, growth of GDP or phase of economic cycles in an economy (Chartblocks, 2020).
4. Prepare a short report on the visual features of an effective chart: As is clear from above picture, the charts are a visual representation for the data as it is very easy and quick to read data visually rather than long tables and numbers. It helps to provide overview and is especially useful when presenting a report or power point, for example, report to the Board of a Company.

While the visual aids are attractive and easy to understand, care must be taken to ensure that the charts are effective. For this, some points must be noted. Firstly, a proper type of chart must be selected keeping in mind the type of data in hand. For example, if we have many data categories, then it is better to use a bar graph instead of a pie chart. Or, if we are presenting continuous data, such as, company’s stock performance, it is better to use line chart instead of bar graph. 

Once a proper type of chart is selected, an effective chart must have a chart title to ensure that the viewer is clear about the context. Also, an effective chart must have well labelled axes along with unit of measurement. Effort must be made to include data labels and values so as to give quick snapshot to the viewer. However, if not possible, legend key or a data table below the chart must be used. Additionally, the chart must be clear and legible to the viewer. To this end, proper formatting, colour palette and font style etc. must be selected so that it is properly visible to the viewer (Karsten, 1925)