This is not to say that there is something wrong with the data you are examining, but just that it might be represented in a way to confuse you. A major role in this confusion is due to write bias. Just like in history, we have biased historians who are most likely to state the narrative they support. Similarly, in writing about anything at all, the personal judgment of the writer can lead you away from the actual point being conveyed.
The type of graph also affects the data being represented. Pie charts are not suitable for every data set, and likewise, bar graphs are not suitable in all circumstances either. Mostly, pie charts are suitable for data comparison within a particular group, whereas bar graphs are suitable for comparing data between various groups.
Also See: 11 Awesome Data Visualizations Way Ahead of Their Time #infographic
The infographic below will further develop your understanding of graphs and interpreting them correctly.
Infographic by: Venngage