Primary and secondary sources of data both have advantages and disadvantages.
Advantages of the secondary sources include:
- Ease of access because the work has been published and readily available. The internet has further made secondary sources easily accessible.
- Secondary sources have a low cost associated with access and use with some online libraries charging less than $10 to access.
Disadvantages of secondary sources include:
- The quality and reliability of the information cannot be easily guaranteed, and at times the information may be misleading.
- Information provided by a secondary source may be outdated.
Advantages of primary sources include:
- Primary sources may provide deeper information such as emotions, socioeconomic status of the source and other metrics that would otherwise be lost in a secondary source.
- A primary source is easily verifiable because one can query the same source.
Disadvantages of primary sources include:
- Primary sources are susceptible to bias and exaggeration.
- Access to primary sources may be expensive and time-consuming.
Any source, whether primary or secondary, will have both values and limitations.
To look for the limitations of the source, you need to look at what factors might make the source less valuable to you. For example, if a source is written by a biased observer it might be limited because it presents only one side of a story. If it is written by someone who is not an expert in that field (perhaps by a journalist rather than by a historian) it might not be as professionally researched as it should be. These types of things would limit the usefulness of the source.
Conversely, some factors might make a source have more value for you. For example, I recently read a book about the Battle of Midway written by Japanese naval officers. If I were writing a paper about the Japanese mentality during WWII, this would be valuable to me because of who wrote it. It might be valuable because it is written by a particularly well-known scholar using detailed and meticulous research. To understand the value of a source, you have to see how closely connected it is to your topic and you have to evaluate it to see if its limitations are too serious to make it useful.