Primary, Secondary & Tertiary Sources

What they are and how they compare (with examples)

By: Derek Jansen (MBA) | Expert Reviewed By: Kerryn Warren (PhD) | January 2023

If you’re new to the wild world of research, you’re bound to encounter the terrible twins, “primary source” and “secondary source” sooner or later. With any luck, “tertiary sources” will get thrown into the mix too! In this post, we’ll unpack both what this terminology means and how to apply it to your research project.

What are primary sources?

Simply put, primary sources (also referred to as primary data) are the original raw materials, evidence or data collected in a study. Primary sources can include interview transcripts, quantitative survey data, as well as other media that provide firsthand accounts of events or phenomena. Primary sources are often considered to be the purest sources because they provide direct, unfiltered data which has not been processed or interpreted in any way.

In addition to the above, examples of primary sources can include

• Results from a social media poll
• Letters written by a historical figure
• Photographs taken during a specific time period
• Government documents such as birth certificates and census records
• Artefacts like clothing and tools from past cultures

Naturally, working with primary data has both benefits and drawbacks. Some of the main advantages include

• Purity: primary sources provide firsthand accounts of events, ideas, and experiences, which means you get access to the rawest, purest form of data.
• Perspective: primary sources allow you to gain a deeper understanding of the perspectives of the people who created them, providing insights into how different groups of people viewed an event or phenomenon.
• Richness: primary data often provide a wealth of detail and nuance that can be missed in secondary data (we’ll cover that shortly). This can provide you with a more complete and nuanced understanding of their topic.

On the flip side, some of the main disadvantages include

• Bias: given their “rawness”, primary sources can often contain biases that can skew or limit your understanding of the issue at hand.
• Inaccessibility: sometimes, collecting fresh primary data can be difficult or even impossible. For example, photographs held in private collections or letters written in a language that you’re not fluent in.
• Fragility: physical artefacts such as manuscripts may be fragile and require special handling, which can make them difficult for you to access or study.
• Limited scope: primary sources often only provide a glimpse of a particular event, person, or period of time, so you may need to rely on multiple primary sources to gain a more complete understanding of a topic.

As you can see, the strengths and weaknesses of primary sources are oftentimes two sides of the same coin. For example, primary data allow you to gain insight into peoples’ unique perspectives, but at the same time, it bakes in a significant level of each participant’s personal bias. So, it’s important to carefully consider what your research aim is and whether it lends itself to this type of data source.

Now that you’ve got a clearer picture of what primary sources/data are, let’s take a look at secondary sources.

What are secondary sources?

Secondary sources are materials that provide an analysis or interpretation of primary sources (primary data). For example, secondary sources of information can include books, journal articles and documentaries. Unlike primary sources (which are raw and uninterpreted), secondary sources provide a distilled, interpreted view of the data.

Other examples of secondary sources include

• A book that provides an analysis of an event
• A biography of a pop icon
• An article that provides an interpretation of a public opinion poll
• A blog post that reviews and compares the performance of competing products

As with primary sources, secondary sources have their own set of pros and cons. Some of the main advantages include:

• Convenience: secondary sources are often easier to access and use than primary sources, as they are widely available in libraries, journal databases, etc.
• Interpretation and synthesis: secondary sources provide a synthesis of the topic of interest, which can help you to quickly understand the most important takeaways from a data set.
• Time-saving: secondary sources can save you time, as you don’t need to analyse primary sources yourself – you can just read summaries or interpretations provided by experts in the field.

At the same time, it’s important to be aware of the disadvantages of secondary sources. Some of the main ones to consider are

• Distance from original sources: secondary sources are based on primary data, but the information has been filtered through the lens of the author, which will naturally carry some level of bias and perhaps even a hidden agenda.
• Limited context: secondary sources may not provide the same level of contextual information or detail as primary sources, which can limit your understanding of the situation and contribute toward a warped understanding.
• Inaccuracies: since secondary sources are the product of human efforts, they may contain inaccuracies or errors, especially if the author has misinterpreted primary data.
• Outdated information: secondary sources may be based on primary sources that are no longer valid or accurate, or they may not take into account more recent research or discoveries.

It’s important to mention that primary and secondary data are not mutually exclusive. In other words, it doesn’t always need to be one or the other. Secondary sources can be used to supplement primary data by providing additional information or context for a particular topic.

For example, if you were researching Martin Luther King Jr., your primary source could be transcripts of the speeches he gave during the civil rights movement. To supplement this information, you could then use secondary sources such as biographies written about him or newspaper articles from the time period in which he was active.

So, once again, it’s important to think about what you’re trying to achieve with your research – that is to say, what are your research aims? As with all methodological choices, your decision to make use of primary or secondary data (or both), needs to be informed by your overall research aims.

Before we wrap up though, it’s important to look at one more source type – tertiary sources.

What are tertiary sources?

Last but not least, we’ve got tertiary sources. Simply put, tertiary sources are materials that provide a general overview of a topic. They often summarise or synthesise information from a combination of primary and secondary sources, such as books, articles, and other documents.

Some examples of tertiary sources include

• Textbooks
• Encyclopedias
• Wikipedia
• Study guides
• Almanacs
• Dictionaries
• Handbooks

Tertiary sources can be useful when you’re just starting to learn about a completely new topic, as they provide an overview of the subject matter without getting too in-depth into specific details. For example, if you’re researching the history of World War II, but don’t know much about it yet, reading an encyclopedia article (or Wikipedia article) on the war would be helpful in providing you with some basic facts and background information.

Tertiary sources are also useful in terms of providing a starting point for citations to primary and secondary source material which can help guide your search for more detailed, credible information on a particular topic. Additionally, these types of resources may also contain lists of related topics or keywords which you can use to find more information regarding your topic of interest.

Importantly, while tertiary sources are a valuable starting point for your research, they’re not ideal sources to cite in your dissertation, thesis or research project. Instead, you should aim to cite high-quality, credible secondary sources such as peer-reviewed journal articles and research papers. So, remember to only use tertiary sources as a starting point. Don’t make the classic mistake of citing Wikipedia as your main source!

Let’s recap

In this post, we’ve explored the trinity of sources: primary, secondary and tertiary.

• Primary sources include the original raw evidence or data that you collect yourself in a study. For example, interview transcripts or statistical data.
• Secondary sources include distilled analyses and interpretations of primary data that someone else collected in their study. For example, journal articles and critical analysis pieces.
• Tertiary sources include materials that provide a general overview of a topic. For example, encyclopedias, study guides and handbooks.
• Each source type has its own set of strengths and weaknesses, and can play a different role within a research project.
• Primary sources and secondary sources are not necessarily mutually exclusive – they can work together to provide a comprehensive view.
• It’s important to ensure that your choice of source (or sources) is guided by and aligned with your research aims.

If you’d like to learn more about primary and secondary research, be sure to check out the rest of the Grad Coach blog here. Alternatively, if you’re looking for hands-on help with your project, take a look at our 1-on-1 private coaching service.