What are two guidelines to determining whether or not information is considered common knowledge?

Common knowledge is information and ideas you deem broadly known by your readers and widely accepted by scholars. 

Information such as the basic biography of a famous author, the dates of a historical event, or widely acknowledged scientific facts, do not need to be cited.

Examples:

The French Revolution began in 1789.

The earth revolves around the sun.

George A. Romero directed Night of the Living Dead.

Proverbs, sayings, and cliches do not need to be cited.

Examples:

A bird in the hand is worth two in the bush.

Curiosity killed the cat.

As a general rule, if you have seen the information repeated multiple times in your reading you do not need to cite.  But, if the information has appeared in only one or two of your sources or when the information is controversial or debated, you must cite the source.

Remember, statistics and the exact words of authors must be cited and given proper documentation.

Examples:

As of 2013, the percent of people who owned their own homes in Arkansas was 65.4%; while nationwide that percent equaled 65.1%.1

Kelly Sultzbach suggests that the "characters’ sensory contact with the natural world shapes the novel’s themes of finding community and coping with the pain and loss necessary for new growth, as well as destabilizing hierarchical relationships between different classes and races of people".2

1. United States Census Bureau. (2013) Housing vacancies and homeownership (CPS/HVS) [Data file].  Retrieved from: //www.census.gov/housing/hvs/data/ann13ind.html      

2. Sultzbach, K. (2009). The chiasmic embrace of the natural world in Eudora Welty's Delta wedding." Southern Literary Journal 42(1),   88-101.       

The only source material that you can use in an essay without attribution is material that is considered common knowledge and is therefore not attributable to one source. Common knowledge is information generally known to an educated reader, such as widely known facts and dates, and, more rarely, ideas or language. Figuring out whether something is common knowledge can be tricky, and it's always better to cite a source if you're not sure whether the information or idea is common knowledge.

Categories of Common Knowledge

Widely known facts

Widely known scientific and historical facts—such as the molecular structure of water (H2O), or that Ernest Manning was the eighth Premier of Alberta—generally count as common knowledge. You can include such facts in your writing without citation and without fear of committing plagiarism. Other facts that count as common knowledge—for instance, that Lap-Chee Tsui, a Canadian geneticist, led a team that identified the gene behind cystic fibrosis—are widely known to some groups of people (professional geneticists) but perhaps not to you. Nevertheless, you would not have to cite the fact about Tsui, since it is common knowledge in the sense that no particular individual discovered this information.

On the other hand, as soon as your discussion includes an individual's thought, research, or analysis, you do have to cite. For example, if you read Gregory Marchildon’s article on Ernest Manning and wrote a paper in which you repeated Marchildon's claim that Manning’s conservative ideals and religious impetus continue to have currency among those challenging universal healthcare, you would need to cite Marchildon as the source of this idea.

Ideas or interpretations are usually not considered common knowledge, unless they are very widely held.

Ideas or interpretations are usually not considered common knowledge, unless they are very widely held. If you read in R.A.C. Parker's history of World War II that British Prime Minister Neville Chamberlain did not have to agree to the 1938 Munich Pact with Hitler, and that he could have chosen an alternate path, you would need to acknowledge the source, since this judgment is Parker's theory rather than a widely agreed upon fact. (Historians disagree on the factors that led Chamberlain to agree to sign on to the Munich Pact.)

Some interpretations or opinions (rather than facts) have entered the realm of common knowledge and need not be cited. If you were to introduce the claim that culture provides a means by which humans adapt to their environments, you would not need to cite a source for this claim, since it is almost universally held by anthropologists. But, if you were unsure that this was the consensus view among anthropologists, you would be best served simply to cite the source. On the whole, opinions or interpretations do not enter the realm of common knowledge as easily as historical or scientific facts.

Verbatim language drawn from a source is rarely common knowledge, unless the formulation is widely known.

You must always provide a citation for quotations you use in your writing. The only—and rare—exceptions to this rule concern well-known quotations that have entered the realm of common knowledge. For example, if you were writing a paper about Justin Trudeau’s swearing-in address, you would need to cite your source for any quotations you used from the speech. However, if in the course of that paper you compared one of Prime Minister Trudeau’s lines to this very well-known phrase from John F. Kennedy's Inaugural Address, "Ask not what your country can do for you—ask what you can do for your country," you would not need to provide a citation for Kennedy’s phrase. However, if you were to analyze Kennedy's speech substantively and quote additional lines, then you would need to cite anything you quoted from his speech so that your readers could confirm the original language of the speech. If you are not sure whether a quotation is common knowledge, cite it.

Adapted from Harvard College Writing Program (2019) //usingsources.fas.harvard.edu/exception-common-knowledge

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The purpose of this policy is to describe a learning environment that respects academic honesty and standards. The policy describes the procedure to follow with a student who does not conduct him/herself in accordance with the guidelines outlined in this policy. The College reserves the right to take appropriate actions when student actions conflict with these expectations.

For more information, see Policy 3-06, Appendix B in the North Island College Policies & Procedures Manual.

Generally, common knowledge is information that someone finds undocumented in at least five credible sources. For example, writing is difficult,” is considered common knowledge in the field of composition studies because at least five credible sources can back the claim up.

Remember the golden rule: When in doubt, just cite.

If the citation proves unnecessary or unnecessarily repetitive your instructor or supervisor will inform you.

es citation work? What is attribution? 

Many professional organizations, including the Modern Language Association (MLA) and the American Psychological Association (APA), have lengthy guidelines for citing sources. We have resources to help you use these guidelines (linked on the sidebar to the left, just underneath this page). But many students are so worried about how to cite a particular source that they never learn how the citation system works. This is often why students end up accidentally plagiarizing. 

Different citation styles have different rules. You should look at the rules for your own (not just the examples that show you how to cite a book chapter). But generally, here is how citation works: 

There are three elements: signal phrase (also called “signposting”), in-text citation (also called “parenthetical citation”), bibliographic citation.  

• A signal phrase is something like “According to Chen Li...” 
• An in-text citation will look like (Li, 2020) or (Li 7) 
• A bibliographic citation will look like: Li, C. (2020). Best practices to avoid plagiarism. Journal of Basic Writing, 42(1), pp. 4-12.  

The signal phrase and the in-text citation show up in the sentences of your paper. The bibliographic citation shows up in the references/works cited/bibliography at the end of your paper, or possibly footnotes at the bottom of each page. You need all three to effectively attribute ideas and words to their proper sources of origin.  

The signal phrase and the in-text citation work together. The signal phrase shows up when you first start talking about a source. It says to the reader “hey! I am drawing on someone else’s idea.” You might use more than one signal phrase if you talk about a source for a few sentences or throughout a paragraph. Then, when you are done talking about that source, the in-text citation ends the sentence. It says to the reader “hey! This is the end of me talking about this source for now. Here is the information you will need to go to the bibliography and find the source I’m talking about.” The bibliographic citation then provides all the information the reader needs to go find the source you looked at. It also tells the reader a number of things before they even do that: the author, how current the source is, its title, and where it was published (like an academic journal, a news site, or a book with lots of chapters). 

Here's an example of what all that looks like put together, using APA:

According to Chen Li (2020), there are six best practices writers can use to avoid plagiarism. These include adopting note-taking habits that focus on attribution, learning about the citation style in question, and "understanding the why behind citation rules" to better apply them (pg. 7).

Reference

Li, C. (2020). Best practices to avoid plagiarism. Journal of Basic Writing, 42(1), pp. 4-12. 

In this example, I opened with a signal phrase that included the author’s name and the year, to tell my reader who I am citing from. Then I summarized Li’s point in the rest of the first sentence. The second sentence includes paraphrase, where I restated her ideas in my own words, and a direct quote in quotation marks, where I used her words exactly. The in-text citation only includes the page number in this case, because I just gave the rest of the citational material a few words earlier. I could have also written (Li, 2020, pg. 7) and that would have been correct. Then I gave all the information about this (made-up) journal article in my references. 

Look at some articles in a journal in your field — maybe class readings, or sources for your own research project. Pay attention to how the authors attribute sources. Look for signal phrases, in-text citations, and bibliographic citations, and try to see the patterns in how these authors use them. Each field is different — this is just one example.  

See also our resource on quoting, paraphrasing, and summarizing. You can’t cite appropriately if you are not sure exactly how you are using source material.